,-,„ .I'.tp.lil , Hi''i If!'"'!:; • ■! '.l!!:ii;it!;!iij! :i!!.;'i"'*'i'i';'i'ii''' '::,:' It is the reason and not the imagination which must ultimately be appealed to. The poet may give us in sublime language an account of the origin and purport of the universe, but in the end it will not satisfy our aesthetic judgment, our idea of harmony and beauty, like the few facts which the scientist may venture to tell us in the same field. The one will agree with all our ex- periences past and present, the other is sure, sooner or later, to contradict our observation because it propounds a dogma, where we are yet far from knowing the whole truth. Our aesthetic judgment demands harmony between the representation and the represented, and in this sense science is often more artistic than modern art. The poet is a valued member of the community, for he is known to be a poet ; his value will increase as he grows to recognise the deeper insight into nature with which modern science provides him. The metaphysician is a poet, often a very great one, but unfortunately he is not known to be a poet, because he strives to clothe his poetry in the language of reason, and hence it follows that he is liable to be a dangerous member of the com- munity. The danger at the present time that meta- physical dogmas may check scientific research is, perhaps, not very great. The day has gone by when the Hegelian philosophy threatened to strangle infant science in Ger- 2 i8 THE GRAMMAR OF SCIENCE many ; — that it begins to languish at Oxford is a proof that it is practically dead in the country of its birth. The day has gone by when philosophical or theological dogmas of any kind can throw back for generations the progress of scientific investigation. There is no restric- tion now on research in any field, or on the publication of the truth when it has been reached. But there is nevertheless a danger which we cannot afford to disregard, a danger which retards the spread of scientific knowledge among the unenlightened, and which flatters obscurantism by discrediting the scientific method. There is a certain school of thought which finds the laborious process by which science reaches truth too irksome ; the temperament of this school is such that it demands a short and easy cut to knowledge, where knowledge can only be gained, if at all, by the long and patient toiling of many groups of workers, perhaps through several centuries. There are various fields at the present day wherein mankind is ignorant, and the honest course for us is simply to confess our ignorance. This ignorance may arise from the want of any proper classification of facts, or because supposed facts are themselves inconsistent, unreal creations of un- trained minds. But because this ignorance is frankly admitted by science, an attempt is made to fence off these fields as ground which science cannot profitably till, to shut them up as a preserve whereon science has no business to trespass. Wherever science has succeeded in ascertaining the truth, there, according to the school we have referred to, are the " legitimate problems of science." Wherever science is yet ignorant, there, we are told, its method is inapplicable ; there some other relation than cause and effect (than the same sequence recurring with the like grouping of phenomena), some new but undefined relationship rules. In these fields, we are told, problems become philosophical and can only be treated by the method of philosophy. The philosophical method is op- posed to the scientific method ; and here, I think, the danger I have referred to arises. We have defined the scientific method to consist in the orderly classification of INTRODUCTORY 19 facts followed by the recognition of their relationship and recurring sequences. The scientific judgment is the judg- ment based upon this recognition and free from personal bias. If this were the philosophical method there would be no need of further discussion, but as we are told the subject-matter of philosophy is not the " legitimate problem of science," the two methods are presumably not identical. Indeed the philosophical method seems based upon an analysis which does not start with the classification of facts, but reaches its judgments by some obscure process of internal cogitation. It is therefore dangerously liable to the influence of individual bias ; it results, as experience shows us, in an endless number of competing and contra- dictory systems. It is because the so-called philosophical method does not, when different individuals approach the same range of facts,^ lead, like the scientific, to practical unanimity of judgment, that science, rather than philo- sophy, offers the better training for modern citizenship. 8 7. — The Ignora7tce of Science It must not be supposed that science for a moment denies the existence of some of the problems which have hitherto been classed as philosophical or metaphysical. On the contrary, it recognises that a great variety of physical and biological phenomena lead directly to these problems. But it asserts that the methods hitherto applied to these problems have been futile, because they have been unscientific. The classifications of facts hitherto made by the system-mongers have been hopelessly in- adequate or hopelessly prejudiced. Until the scientific study of psychology, both by observation and experiment, has advanced immensely beyond its present limits — and this may take generations of work — science can only answer to the great majority of " metaphysical " problems, 1 This statement by no means denies the existence of many moot points, unsettled problems in science ; but the genuine scientist admits that they are unsolved. As a rule they lie just on the frontier line between knowledge and ignorance, where the pioneers of science are pushing forward into unoccupied and difficult country. 20 THE GRAMMAR OF SCIENCE " I am ignorant." Meanwhile it is idle to be impatient or to indulge in system-making. The cautious and laborious classification of facts must have proceeded much further than at present before the time will be ripe for drawing conclusions. Science stands now with regard to the problems of life and mind in much the same position as it stood with regard to cosmical problems in the seventeenth century. Then the system-mongers were the theologians, who declared that cosmical problems were not the " legitimate problems of science." It was vain for Galilei to assert that the theologians' classification of facts was hopelessly inadequate. In solemn congregation assembled they settled that : — " The doctrine that the earth is neither the centre of the zmiverse nor ivnnovable, but moves even with a daily rotation, is absurd, and both philosophically and theologically false, and at the least an error of faith." ^ It took nearly two hundred years to convince the whole theological world that cosmical problems were the legitimate problems of science and science alone, for in I 8 1 9 the books of Galilei, Copernicus, and Keppler were still upon the index of forbidden books, and not till 1822 was a decree issued allowing books teaching the motion of the earth about the sun to be printed and published in Rome ! I have cited this memorable example of the absurdity which arises from trying to pen science into a limited field of thought, because it seems to me exceedingly suggestive of what must follow again, if any attempt, philosophical or theological, be made to define the " legiti- mate problems of science." Wherever there is the slightest possibility for the human mind to know, there is a legitimate problem of science. Outside the field of actual knowledge can only lie a region of the vaguest opinion ^ "Terrain iion esse centrum Mundi, nee immobilem, sed ?noveri motu etiam diurtio, est item propositio absurda, et falsa in Philosophia, et Theoligice C07tsiderata ad minus erronea in fide'''' (Congregation of Prelates and Cardinals, June 22, 1633). INTRODUCTORY 21 and imagination, to which unfortunately men too often, but still with decreasing prevalence, pay higher respect than to knowledge. We must here investigate a little more closely what the man of science means when he says, " Here I am ignorant^ In the first place, he does not mean that the method of science is necessarily inapplicable, and accordingly that some other method is to be sought for. In the next place, if the ignorance really arises from the inadequacy of the scientific method, then we may be quite sure that no other method whatsoever will reach the truth. The ignorance of science means the enforced ignorance of mankind. I should be sorry myself to assert that there is any field of either mental or physical perceptions which science may not in the long course of centuries enlighten. Who can give us the assurance that the fields already occupied by science are alone those in which knowledge is possible ? Who, in the words of Galilei, is willing to set limits to the human intellect ? It is true that this view is not held by several leading scientists, both in this country and Germany. They are not content with saying, " We arc ignorant," but they add, with regard to certain classes of facts, " Mankind must always be ignorant." Thus in England Professor Huxley has invented the term Agnostic, not so much for those who are ignorant as for those who limit the possibility of knowledge in certain fields. In Germany Professor E. du Bois-Reymond has raised the cry, " Ignorabiinus " (" We shall be ignorant "), and both his brother and he have undertaken the difficult task of demonstrating that with regard to certain problems human knowledge is impossible.^ We must, however, note that in these cases we are not concerned with the limitation of the scientific method, but with the denial of the possibility that any method whatever can lead to knowledge. Now I venture to think that there is great danger in this cry, " We sJiall be ignorant." To cry " We are ignorant " is safe and 1 See especially Paul du Bois-Reymond : Ueber die Gnindlagen der Erkenntniss in den exacten Wissenschaften. Tubingen, 1890. 22 THE GRAMMAR OF SCIENCE healthy, but the attempt to demonstrate an endless futurity of ignorance appears a modesty which approaches despair. Conscious of the past great achievements and the present restless activity of science, may we not do better to accept as our watchword that sentence of Galilei : " Who is willing to set limits to the human intellect?" — interpreting it by what evolution has taught us of the continual growth of man's intellectual powers. Scientific ignorance may, as I have remarked (p. i 8), either arise from an insufficient classification of facts, or be due to the unreality of the facts with which science has been called upon to deal. Let us take, for example, fields of thought which were very prominent in mediaeval times, such as alchemy, astrology, witchcraft. In the fifteenth century nobody doubted the " facts " of astrology and witchcraft. Men were ignorant as to how the stars exerted their influence for good or ill ; they did not know the exact mechanical process by which all the milk in a village was turned blue by a witch. But for them it was nevertheless a fact that the stars did influence human lives, and a fact that the witch had the power of turning the milk blue. Have we solved the problems of astrology and witchcraft to-day ? Do we now know how the stars influence human lives, or how witches turn milk blue ? Not in the least. We have learnt to look upon the facts themselves as unreal, as vain imaginings of the untrained human mind ; we have learnt that they could not be described scientifically because they involved notions which were in themselves contradictory and absurd. With alchemy the case was somewhat different. Here a false classification of real facts was combined with inconsistent sequences — that is, sequences not deduced by a rational method. So soon as science entered the field of alchemy with a true classifi- cation and a true method, alchemy was converted into chemistry and became an important branch of human knowledge. Now it will, I think, be found that the fields of inquiry, where science has not yet penetrated and where the scientist still confesses ignorance, are very like the INTRODUCTORY 23 alchemy, astrology, and witchcraft of the Middle Ages. Either they involve facts which are in themselves unreal — conceptions which are self-contradictory and absurd, and therefore incapable of analysis by the scientific or any other method, — or, on the other hand, our ignorance arises from an inadequate classification and a neglect of scientific method. This is the actual state of the case with those mental and spiritual phenomena which are said to lie outside the proper scope of science, or which appear to be disregarded by scientific men. No better example can be taken than the range of phenomena which are entitled Spiritualism. Here science is asked to analyse a series of facts which are to a great extent unreal, which arise from the vain imasfinincfs of untrained minds and from atavistic tendencies to superstition. So far as the facts are of this character, no account can be given of them, because, like the witch's supernatural capacity, their unreality will be found at bottom to make them self- contradictory. Combined, however, with the unreal series of facts are probably others, connected with hypnotic and other conditions, which are real and only incomprehensible because there is as yet scarcely any intelligent classification or true application of scientific method. The former class of facts will, like astrology, never be reduced to law, but will one day be recognised as absurd ; the other, like alchemy, may grow step by step into an important branch of science. Whenever, therefore, we are tempted to desert the scientific method of seeking truth, whenever the silence of science suggests that some other gateway must be sought to knowledge, let us inquire first whether the elements of the problem, of whose solution we are ignorant, may not after all, like the facts of witchcraft, arise from a superstition, and be self- contradictory and incompre- hensible because they are unreal. If on inquiry we ascertain that the facts cannot possibly be of this class, we must then remember that it may require long ages of increasing toil and investigation before the classification of the facts can be so complete 24 THE GRAMMAR OF SCIENCE that science can express a definite judgment on their relationship. Let us suppose that the Emperor Karl V. had said to the learned of his day : " I want a method by which I can send a message in a few seconds to that new world, which my mariners take weeks in reaching. Put your heads together and solve the problem." Would they not undoubtedly have replied that the problem was impossible ? To propose it would have seemed as ridicu- lous to them as the suggestion that science should straightway solve many problems of life and mind seems to the learned of to-day. It required centuries spent in the discovery and classification of new facts before the Atlantic cable became a possibility. It may require the like or even a longer time to unriddle those psychical and biological enigmas to which I have referred ; but he who declares that they can never be solved by the scientific method is to my mind as rash as the man of the early sixteenth century would have been had he declared it utterly impossible that the problem of talking across the Atlantic Ocean should ever be solved. 8 8. — The Wide Domain of Science If I have put the case of science at all correctly, the reader will have recognised that modern science does much more than demand that it shall be left in undis- turbed possession of what the theologian and metaphysician please to term its " legitimate field." It claims that the whole range of phenomena, mental as well as physical — the entire universe — is its field. It asserts that the scientific method is the sole gateway to the whole region of knowledge. The word science is here used in no narrow sense, but applies to all reasoning about facts which proceeds, from their accurate classification, to the appreciation of their relationship and sequence. The touchstone of science is the universal validity of its results for all normally constituted and duly instructed minds. Because the glitter of the great metaphysical systems becomes dross when tried by this touchstone, we are INTRODUCTORY 25 compelled to classify them as interesting works of the imagination, and not as solid contributions to human knowledge. Although science claims the whole universe as its field, it must not be supposed that it has reached, or ever can reach, complete knowledge in every department. Far from this, it confesses that its ignorance is more widely extended than its knowledge. In this very confession of ignorance, however, it finds a safeguard for future progress. Science cannot give its consent to man's development being some day again checked by the barriers which dogma and myth are ever erecting round territory that science has not yet effectually occupied. It cannot allow theologian or metaphysician, those Portuguese of the intellect, to establish a right to the foreshore of our present ignorance, and so hinder the settlement in due time of vast and yet unknown continents of thought. In the like barriers erected in the past science finds some of the greatest difficulties in the way of intellectual progress and social advance at the present. It is the want of impersonal judgment, of scientific method, and of accurate insight into facts, a want largely due to a non-scientific training, which renders clear thinking so rare, and random and irresponsible judgments so common, in the mass of our citizens to-day. Yet these citizens, owing to the growth of democracy, have graver problems to settle than probably any which have confronted their forefathers since the days of the Revolution. S g. — TJie Second Claim of Science Hitherto the sole ground on which we have considered the appeal of modern science to the citizen is the indirect influence it has upon conduct owing to the more efficient mental training which it provides. But we have further to recognise that science can on occasion adduce facts having far more direct bearing on social problems than any theory of the state propounded by the philosophers from the days of Plato to those of Hegel. I cannot bring 26 THE GRAMMAR OF SCIENCE home to the reader the possibility of this better than by citing some of the conclusions to which the theory of heredity elaborated by the German biologist Weismann introduces us, Weismann's theory lies on the borderland of scientific knowledge ; his results are still open to dis- cussion, his conclusions to modification.^ But to indicate the manner in which science can directly influence conduct, we will assume for the time being Weismann's main con- clusion to be correct. One of the chief features of his theory is the non-inheritance by the offspring of character- istics acquired by the parents in the course of life. Thus good or bad habits acquired by the father or mother in their lifetime are not inherited by their children. The effects of special training or of education on the parents have no direct influence on the child before birth. The parents are merely trustees who hand down their com- mingled stocks to their offspring. From a bad stock can come only bad offspring, and if a member of such a stock is, owing to special training and education, an exception to his family, his offspring will still be born with the old taint," Now this conclusion of Weismann's — if it be valid, and all we can say at present is that the arguments in favour of it are remarkably strong — radically affects our judgment on the moral conduct of the individual, and on the duties of the state and society towards their degenerate members. No degenerate and feeble stock will ever be converted into healthy and sound stock by the accumulated effects of education, good laws, and 1 His theory of the "continuity of the germ plasm" is in many respects open to question, but his conclusion as to acquired characteristics being uninherited stands on firmer ground. See Weismann, Essays o?t Heredity and Kindred Biological Problems, Oxford, 1889. A good criticism will be found in C. LI. Morgan's Animal Life and Intelligence, chap. v. ; a sum- mary in W. P. Ball's Are the Effects of Use and Disuse Inhei-ited? Tlie reader should also consult P. Geddes and J. A. Thomson, The Evolution of Sex, and a long discussion in Nature, vols. xl. and xli, {sub indice, Weismann, Heredity). 2 Class, poverty, localisation do much to approximately isolate stock, to aggregate the unfit even in modern civilisation. The mingling of good and bad stock due to dispersion is not to be commended, for it degenerates the good as much as it improves the bad. What we need is a check to the fertility of the inferior stocks, and this can only arise with new social habits and new conceptions of the social and the anti-social in conduct. INTRODUCTORY 27 sanitary surroundings. Such means may render the individual members of the stock passable if not strong members of society, but the same process will have to be gone through again and again with their offspring, and this in ever-widening circles, if the stock, owing to the conditions in which society has placed it, is able to increase in numbers. The suspension of that process of natural selection which in an earlier struggle for existence crushed out feeble and degenerate stocks, may be a real danger to society, if society relies solely on changed environment for converting its inherited bad into an inheritable good. If society is to shape its own future — if we are to replace the stern processes of natural law, which have raised us to our present high standard of civilisation, by milder methods of eliminating the unfit — then we must be peculiarly cautious that in following our strong social instincts we do not at the same time weaken society by rendering the propagation of bad stock more and more easy. If the views of VVeismann be correct — if the bad man can by the influence of education and surroundings be made good, but the bad stock can never be converted into good stock — then we see how grave a responsibility is cast at the present day upon every citizen, who directly or indirectly has to consider problems relating to the state endowment of education, the revision and administration of the Poor Law, and, above all, the conduct of public and private charities annually disposing of immense resources. In all problems of this kind the blind social instinct and the individual bias at present form extremely strong factors of our judgment. Yet these very problems are just those which, affecting the whole future of our society, its stability and its efficiency, require us, as good citizens, above all to understand and obey the laws of healthy social development. The example we have considered will not be futile, nor its lessons worthless, should Weismann's views after all be inaccurate. It is clear that in social problems of the kind I have referred to, the laws of heredity, whatever 28 THE GRAMMAR OF SCIENCE they may be, must profoundly influence our judgment. The conduct of parent to child, and of society to its anti- social members, can never be placed on sound and perma- nent bases without regard be paid to what science has to tell us on the fundamental problems of inheritance. The " philosophical " method can never lead to a real theory of morals. Strange as it may seem, the laboratory experiments of a biologist may have greater weight than all the theories of the state from Plato to Hegel ! The scientific classification of facts, biological or historical, the observation of their correlation and sequence, the resulting absolute, as opposed to the individual judgment — these are the sole means by which we can reach truth in such a vital social question as that of heredity. In these con- siderations alone there appears to be sufficient justification for the national endowment of science, and for the universal training of our citizens in scientific methods of thought. Each one of us is now called upon to give a judgment upon an immense variety of problems, crucial for our social existence. If that judgment confirms measures and conduct tending to the increased welfare of society, then it may be termed a moral, or, better, a social judgment. It follows, then, that to ensure a judg- ment's being moral, method and knowledge are essential to its formation. It cannot be too often insisted upon that the formation of a moral judgment — that is, one which the individual is reasonably certain will tend to social welfare — does not depend solely on the readiness to sacrifice individual gain or comfort, or on the impulse to act unselfishly : it depends in the first place on know- ledge and method. The first demand of the state upon the individual is -not for self-sacrifice, but for self-develop- ment. The man who gives a thousand pounds to a vast and vague scheme of charity may or may not be acting socially ; his self-sacrifice, if it be such, proves nothing ; but the man who gives a vote, either directly or even indirectly, in the choice of a representative, after forming a judgment based upon knoivlcdge, is undoubtedly acting socially, and is fulfilling a higher standard of citizenship. INTRODUCTORY 29 S 10. — The Third Claim of Science Thus far I have been more particularly examining the influence of science on our treatment of social problems. I have endeavoured to point out that science cannot legitimately be excluded from any field of investigation after truth, and that, further, not only is its method essential to good citizenship, but that its results bear closely on the practical treatment of many social diffi- culties. In this I have endeavoured to justify the state endowment and teaching of pure science as apart from its technical applications. If in this justification I have laid most stress on the advantages of scientific method — on the training which science gives us in the appreciation of evidence, in the classification of facts, and in the elimina- tion of personal bias, in all that may be termed exactness of mind — we must still remember that ultimately the direct influence of pure science on practical life is enor- mous. The observations of Newton on the relation between the motions of a falling stone and the moon, of Galvani on the convulsive movements of frogs' legs in contact with iron and copper, of Darwin on the adaptation of woodpeckers, of tree-frogs, and of seeds to their sur- roundings, of Kirchhoff on certain lines which occur in the spectrum of sunlight, of other investigators on the life- history of bacteria — these and kindred observations have not only revolutionised our conception of the universe, but they have revolutionised, or are revolutionising, our practical life, our means of transit, our social conduct, our treatment of disease. What at the instant of its dis- covery appears to be only a sequence of purely theoretical interest, becomes the basis of discoveries which in the end profoundly modify the conditions of human life. It is impossible to say of any result of pure science that it will not some day be the starting-point of wide-reaching technical applications. The frogs' legs of Galvani and the Atlantic cable seem wide enough apart, but the former was the starting-point of the series of investigations which ended in the latter. In the recent discovery of Hertz 30 THE GRAMMAR OF SCIENCE that the action of electro-magnetism is propagated in waves Hke h'ght — in his confirmation of Maxwell's theory that light is only a special phase of electro-magnetic action — we have a result which, if of striking interest to pure science, seems yet to have no immediate practical application.^ But that man would indeed be a bold dogmatist who would venture to assert that the results which may ultimately flow from this discovery of Hertz's will not, in a generation or two, do more to revolutionise life than the frogs' legs of Gal van i achieved when they led to the perfection of the electric telegraph. § I I. — Science and the Imagination There is another aspect from which it is right that we should regard pure science — one that makes no appeal to its utility in practical life, but touches a side of our nature which the reader may have thought that I have entirely neglected. There is an element in our being which is not satisfied by the formal processes of reasoning ; it is the imaginative or sesthetic side, the side to which the poets and philosophers appeal, and one which science cannot, to be scientific, disregard. We have seen that the imagination must not replace the reason in the deduc- tion of relation and law from classified facts. But, none the less, disciplined imagination has been at the bottom of all great scientific discoveries. All great scientists have, in a certain sense, been great artists ; the man with no imagination may collect facts, but he cannot make great discoveries. If I were compelled to name the Englishmen who during our generation have had the widest imaginations and exercised them most beneficially, I think I should put the novelists and poets on one side and say Michael Faraday and Charles Darwin. Now it is very needful to understand the exact part imagination plays in pure science. We can, perhaps, best achieve this result by considering the following proposition : Pure science has a further strong claim upon us on ^ Even since this sentence was written a first and initially quite unexpected application to practical life has arisen in wireless telegraphy ! INTRODUCTORY 31 account of the exercise it gives to the imaginative faculties and the gratification it provides for the aesthetic judgment. The exact meaning of the terms " scientific fact " and " scientific law " will be considered in later chapters, but for the present let us suppose an elaborate classification of such facts has been made, and their relationships and sequences carefully traced. What is the next stage in the process of scientific investigation ? Undoubtedly it is the use of the imagination. The discovery of some single statement, some brief fornmla from which the whole group of facts is seen to flow, is the work, not of the mere cataloguer, but of the man endowed with creative imagination. The single statement, the brief formula, the few words of which replace in our minds a wide range of relationships between isolated phenomena, is what we term a scientific law. Such a law, relieving our memory from the burden of individual sequences, enables us, with the minimum of intellectual fatigue, to grasp a vast complexity of natural or social phenomena. The discovery of law is therefore the peculiar function of the creative imagination. But this imagination has to be a disciplined one. It has in the first place to appreciate the whole range of facts, which require to be resumed in a single statement ; and then when the law is reached — often by what seems solely the inspired imagination of genius — it must be tested and criticised by its discoverer in every conceivable way, till he is certain that the imagination has not played him false, and that his law is in real agreement with the whole group of phenomena which it resumes. Herein lies the key-note to the scientific use of the imagination. Hundreds of men have allowed their imagination to solve the universe, but the men who have contributed to our real understanding of natural phenomena have been those who were unstinting in their application of criticism to the product of their imaginations. It is such criticism which is the essence of the scientific use of the imagination, which is, indeed, the very life-blood of science.-^ ^ La critique est la vie de la sciences, says Victor Cousin. 32 THE GRAMMAR OF SCIENCE No less an authority than Faraday writes : — " The world little knows how many of the thoughts and theories which have passed through the mind of a scientific investigator have been crushed in silence and secrecy by his own severe criticism and adverse examina- tion ; that in the most successful instances not a tenth of the suggestions, the hopes, the wishes, the preliminary conclusions have been realised." § 1 2. — The MetJiod of Science Illustrated The reader must not think that I am painting any ideal or purely theoretical method of scientific discovery. He will find the process described above accurately depicted by Darwin himself in the account he gives us of his discovery of the law of natural selection. After his return to England in 1837, he tells us,^ it appeared to him that : — " By collecting all facts which bore in any way on the variation of animals and plants under domestication and nature, some light might perhaps be thrown on the whole subject. My first note-book was opened in July 1837. I worked on true Baconian principles,^ and, without any theory, collected facts on a wholesale scale, more especially with respect to domesticated productions, by printed inquiries, by conversation with skilful breeders and ^ The Life and Letters of Charles Dan.vin, vol. i. p. Zt^. 2 It is from men like Laplace and Darwin, who have devoted their lives to natural science, rather than from workers in the pure field of conception, like Mill and Stanley Jevons, that we must seek for a true estimate of the Baconian method. Beside Darwin's words we may! place those of Laplace on Bacon : — " II a donne pour la recherche de la verite, le precepte et non I'exemple. Mais en insistant avec toute la force de la raison et de I'eloquence, sur la necessite d'abandonner les subtilites insignifiantes de I'ecole, pour se livrer aux observations et aux experiences, et en indiquant la vraie methode de s'elever aux causes generales des phenomenes, ce grand philosophe a con- tribue aux progies immenses que I'esprit humain a faits dans le beau siecle oil il a termine sa carriere " (" Theorie analytique des Probabilites," CEicvres, t. vii. p. clvi.). The carpenter who uses a tool is a better judge of its efficiency than the smith who forges it. For a good sketch of the estimation in which Bacon was held by his scientific contemporaries see the introduction to Prof. Fowler's edition of the Novum Orza)iii?n. INTRODUCTORY 33 gardeners, and by extensive reading. When I see the Hst of books of all kinds which I read and abstracted, including whole series of Journals and Transactions, I am surprised at my own industry. I soon perceived that selection was the keystone of man's success in making useful races of animals and plants. But how selection could be applied to organisms living in a state of nature remained for some time a mystery to me." Here we have Darwin's scientific classification of facts, what he himself terms his " systematic inquiry." Upon the basis of this systematic inquiry comes the search for a law. This is the work of the imagination ; the inspira- tion in Darwin's case being apparently due to a perusal of Malthus' Essay on Population. But Darwin's imagina- tion was of the disciplined scientific sort. Like Turgot, he knew that if the first thing is to invent a system, then the second is to be disgusted with it. Accordingly there followed the period of self-criticism, which lasted four or five years, and it was no less than nineteen years before he gave the world his discovery in its final form. Speak- ing of his inspiration that natural selection was the key to the mystery of the origin of species, he says : — " Here, then, I had at last got a theory by which to work ; but I was so anxious to avoid prejudice, that I determined not for some time to write even the briefest sketch of it. In June 1842 {i.e. four years after the inspiration), I first allowed myself the satisfaction of writing a very brief abstract of my theory in pencil in 3 5 pages ; and this was enlarged during the summer of i 844 into one of 230 pages, which I had fairly copied out and still possess." Finally an abstract from Darwin's manuscript was published with Wallace's Essay in 1858, and the Origin of Species appeared in 1859- In like manner, Newton's imagination was only paral- leled by that power of self-criticism which led him to lay aside a demonstration touching the gravitation of the moon for nearly eighteen years, until he had supplied a missing link in his reasoning. But our details of Newton's 34 THE GRAMMAR OF SCIENCE life and discoveries are too meagre for us to see his method as closely as we can Darwin's, and the account I have given of the latter is amply sufficient to show the actual application of scientific method, and the real part played in science by the disciplined use of the imagination.^ ^ 13. — Science and the Aesthetic Judgmetit We are justified, I think, in concluding that science does not cripple the imagination, but rather tends to exercise and discipline its functions. We have still, how- ever, to consider another phase of the relationship of the imaginative faculty to pure science. When we see a great work of the creative imagination, a striking picture or a powerful drama, what is the essence of the fascination it exercises over us ? Why does our aesthetic judgment pronounce it a true work of art ? Is it not because we 1 That the classification of facts is often largely guided by the imagination as well as the reason must be fully admitted. At the same time, an accurate classification, either due to the scientist himself or to previous workers, must exist in the scientist's mind before he can proceed to the discovery of law. Here, as elsewhere, the reader will find that I differ very widely from Stanley Jevons' views as developed in his Principles of Science. I cannot but feel that chapter xxvi. of that work would have been recast had the author been acquainted with Darwin's method of procedure. The account given by Jevons of the Newtonian method seems to me to lay insufficient stress upon the fact that Newton had a wide acquaintance with physics before he pro- ceeded to use his imagination and test his theories by experiment — that is, to a period of self-criticism. The reason that pseudo-scientists cumber the reviewer's table with idle theories, often showing great imaginative power and ingenuity, is not solely want of self-criticism. Their theories, as a rule, are not such as the scientist himself would ever propound and criticise. Their impossibility is obvious, because their propounders have neither formed for themselves, nor been acquainted with others' classifications of the groups of facts which their theories are intended to summarise. Newton and Faraday started with full knowledge of the classifications of physical facts which had been formed in their own days, and proceeded to further conjoint theorising and classifying. Bacon, of whom Stanley Jevons is, I think, unreasonably contemptuous, lived at a time when but little had been done by way of classification, and he was wanting in the scientific imagination of a Newton or a Faraday. Hence the barrenness of his method in his own hands. The early history of the Royal Society's meetings shows how essentially the period of collection and classification of facts preceded that of valuable theory. With Stanley Jevons' last chapter on The Liinits of Scientific AletJiod the present writer can only express his complete disagreement ; many of its arguments appear to him unscientific, if it were not better to term them anti- scientific. INTRODUCTORY 35 find concentrated into a brief statement, into a simple formula or a few symbols, a wide range of human emotions and feelings ? Is it not because the poet or the artist has expressed for us in his representation the true relationship between a variety of emotions, which we, in a long course of experience, have been consciously or unconsciously classifying? Does not the beauty of the artist's work lie for us in the accuracy with which his symbols resume innumerable facts of our past emotional experience ? The aesthetic judgment pronounces for or against the inter- pretation of the creative imagination according as that interpretation embodies or contradicts the phenomena of life, which we ourselves have observed.^ It is only satisfied when the artist's formula contradicts none of the emotional phenomena which it is intended to resume. If this account of the aesthetic judgment be at all a true one, the reader will have remarked how exactly parallel it is to the scientific judgment.^ But there is really more than mere parallelism between the two. The laws of science are, as we have seen, products of the creative imagination. They are the mental interpretations — the formulae under which we resume wide ranges of phenomena, the results of observation on the part of ourselves or of our fellow-men. The scientific interpretation of phenomena, the scientific account of the universe, is therefore the only one which can permanently satisfy the aesthetic judgment, for it is the only one which can never be entirely contra- dicted by our observation and experience. It is necessary to strongly emphasise this side of science, for we are frequently told that the growth of science is destroying the beauty and poetry of life. It is undoubtedly rendering many of the old interpretations of life meaningless, because it demonstrates that they are false to the facts which they profess to describe. It does not follow from this, however, 1 How important a part length and variety of emotional experience play in the determination of the cesthetic judgment is easily noted by investigating the favourite authors and pictures of a few friends of diverse ages and conditions. 2 The curious reader may be referred to Wordsworth's " General View of Poetry" in his preface to the Lyrical Ballads, 1S15. 36 ■ THE GRAMMAR OF SCIENCE that the aesthetic and scientific judgments are opposed ; the fact is, that with the growth of our scientific know- ledge the basis of the aesthetic judgment is changing and must change. There is more real beauty in what science has to tell us of the chemistry of a distant star, or in the life-history of a protozoon, than in any cosmogony pro- duced by the creative imagination of a pre-scientific age. By " more real beauty " we are to understand that the aesthetic judgment will find more satisfaction, more permanent delight, in the former than in the latter. It is this continual gratification of the aesthetic judgment which is one of the chief delights of the pursuit of pure science. § 1 4. — TJie Fourth Claim of Science There is an insatiable desire in the human breast to resume in some short formula, some brief statement, the facts of human experience. It leads the savage to " account " for all natural phenomena by deifying the wind and the stream and the tree. It leads civilised man, on the other hand, to express his emotional experience in works of art, and his physical and mental experience in the formulae or so-called laws of science. Both works of art and laws of science are the product of the creative imagination, both afford material for the gratification of the aesthetic judgment. It may seem at first sight strange to the reader that the laws of science should thus be associated with the creative imagination in man rather than with the physical world outside him. But, as we shall see in the course of the following chapters, the laws of science are products of the human mind rather than factors of the external world. Science endeavours to provide a mental resume of the universe, and its last great claim to our support is the capacity it has for satisfying our cravings for a brief description of the history of the world. Such a brief description, a formula resuming all things, science has not yet found and may probably never find, but of this we may feel sure, that its method of seeking for one is the sole possible method, and that the INTRODUCTORY 37 truth it has reached is the only form of truth which can permanently satisfy the aesthetic judgment. For the present, then, it is better to be content with the fraction of a right solution than to beguile ourselves with the whole of a wrong solution. The former is at least a step towards the truth, and shows us the direction in which other steps may be taken. The latter cannot be in entire accordance with our past or future experience, and will therefore ultimately fail to satisfy the aesthetic judgment. Step by step that judgment, restless under the growth of positive knowledge, has discarded creed after creed, and philosophic system after philosophic system. Surely we might now be content to learn from the pages of history that only little by little, slowly line upon line, man, by the aid of organised observation and careful reasoning, can hope to reach knowledge of the truth, that science, in the broadest sense of the word, is the sole gateway to a knowledge which can harmonise with our past as well as with our possible future experience. As Clifford puts it, " Scientific thought is not an accompaniment or condition of human progress, but human progress itself" SUMMARY 1. The scope of science is to ascertain truth in every possible branch of knowledge. There is no sphere of inquiry which lies outside the legitimate field of science. To draw a distinction between the scientific and philosophical fields is obscurantism. 2. The scientific method is mar-ked by the following features : — (a) Careful and accurate classification of facts and observation of their correlation and sequence ; (b) the discovery of scientific laws by aid of the creative imagina- tion ; ((') self-criticism and the final touchstone of equal validity for all normally constituted minds. 3. The claims of science to our support depend on : — {a) The efficient mental training it provides for the citizen ; (3) the light it brings to bear on many important social problems ; (r) the increased comfort it adds to practical life ; (d) the permanent gratification it yields to the aesthetic judgment. LITERATURE Bacon, Francis. — ^Novum Organum, London, 1620. A good edition by T. Fowler. Clarendon Press, 1878. 38 THE GRAMMAR OF SCIENCE Bois-Reymond, E. du. — Ueber die Grenzen des Naturerkennens. Veit and Co., Leipzig, 1876. Bois-Reymond, P. du. — Ueber die Grundlagen der Erkenntniss in den exacten Wissenschaften. H. Laupp, Tiibingen, 1890. Clifford, W. K. — Lectures and Essays. Macmillan, 1879. ("Aims and Instruments of Scientific Thought," "The Ethics of Belief," and " Virchow on the Teaching of Science.") Haeckel, E.— Freie Wissenschaft und freie Lehre. E. Schweizerbart, Stuttgart, 1878. Haldane, J. S. — "Life and Mechanism," Mind, ix. pp. 27-47; also Nature, vol. xxvii., 1883, p. 561, vol. xxiv., 1886, p. 73; and also Haldane, R. B., Proceedings of the Aristotelean Society, 1891, vol. i. No. 4, part i. pp. 22-27. Helmholtz, H. — On the Relation of the Natural Sciences to the Totality of the Sciences, translated by C. H. Schaible. London, 1869. This occurs also in the Popular Lectures, translated by Atkinson and others, First Series, p. i. Longmans, 1881. Herschel, Sir John. — A Preliminary Dissertation on Natural Philosophy. London, 1830. Jevons, W. Stanley. — The Principles of Science : A Treatise on Logic and Scientific Method, 2nd ed. Macmillan, 1877. Pearson, K. — ^The Ethic of Freethought : A Selection of Essays and Lectures ("The Enthusiasm of the Market-place and of the Study"). Fisher Unwin, 1888. The Chances of Death and other Studies in Evolution, vol. i. ("Science and Politics" and "Reaction"). Edward Arnold, 1897. Virchow, R. — Die Freiheit der Wissenschaft im modernen Staat (Versamm- lung deutscher Naturforscher). Miinchen, 1877. CHAPTER II THE FACTS OF SCIENCE S I . — T]ie Reality of Things In our first chapter we have frequently spoken of the classification of facts as the basis of the scientific method ; we have also had occasion to use the words real and unreal, universe and phcnojuenon. It is proper, therefore, that before proceeding further we should endeavour to clear up our ideas as to what these terms signify. We must strive to define a little more closely in what the material of science consists. We have seen that the legitimate field of science embraces all the mental and physical facts of the universe. But what are these facts in themselves, and what is for us the criterion of their reality? Let us start our investigation with some " external object," and as apparent simplicity will be satisfied by taking a familiar requisite of the author's calling, namely, a blackboard, let us take it.^ We find an outer rect- angular frame of brownish-yellow colour, which on closer inspection we presume to be wood, surrounding an inner fairly smooth surface painted black. We can measure a certain height, thickness, and breadth, we notice a certain degree of hardness, weight, resistance to breaking, and, if we examine further, a certain temperature, for the board feels to us cold or warm. Now although the black- board at first sight appears a very simple object, we see 1 The blackboard as an "object-lesson" is such a favourite instance with the writer, that the reader will perhaps pardon him the use of it here. Seine Mundart klebt jedem an. 40 THE GRAMMAR OF SCIENCE that it at once leads us up to a very complex group of properties. In common talk we attribute all these properties to the blackboard, but when we begin to think over the matter carefully we shall find that the real link between them is by no means so simple as it seems to be. To begin with, I receive certain impressions of size and shape and colour by means of my organs of sight, and these enable me to pronounce with very considerable certainty that the object is a blackboard made of wood and coated with paint, even before I have touched or measured it. I infer that I shall find it hard and heavy, that I could if I pleased saw it up, and that I should find it to possess various other properties which I have learnt to associate with wood and paint. These inferences and associations are something which I add to the sight- impressions, and which I myself contribute from my past experience and put into the object — blackboard. I might have reached my conception of the blackboard by impres- sions of touch and not by those of sight. Blindfolded I might have judged of its size and shape, of its hardness and surface texture, and then have inferred its probable use and appearance, and associated with it all blackboard characteristics. In both cases it must be noted that 2. sine qua non of the existence of an actual blackboard is some immediate sense-impression to start with. The sense- impressions which determine the reality of the external object may be very few indeed, the object may be largely constructed by inferences and associations, but some sense- impressions there must be if I am to term the object real, and not a product merely of my imagination. The existence of a certain number of sense-impressions leads me to infer the possibility of my receiving others, and this possibility I can, if I please, put to the test. I have heard of the Capitol at Washington, and although I have never been to America, I am convinced of the reality of America and the Capitol — that is, I believe certain sense-impressions would be experienced by me if I put myself in the proper circumstances. In this case I have had indirect sense-impressions, contact with THE FACTS OF SCIENCE 41 Americans, and with ships and chattels coming from America, which lead me to believe in the " reality " of America and of what my eyes or ears have told me of its contents. In constructing the Capitol it is clear that past experience of a variety of kinds is largely drawn upon. But it must be noted that this past experience is itself based upon sense-impressions of one kind or another. These sense-impressions have been as it were stored in the memory. A sense-impression, if sufficiently strong, leaves in our brain some more or less permanent trace of itself, which is rendered manifest in the form of association whenever an immediate sense-impression of a like kind recurs. The stored effects of past sense-impressions form to a great extent what we are accustomed to speak of as an " external object." On this account such an object must be recognised as largely constructed by ourselves ; we add to a greater or less number of immediate sense-impressions an associated group of stored sense-impressions. The proportion of the two contribu- tions will depend largely on the keenness of our organs of sense and on the length and variety of our experience. Owing to the large amount we ourselves contribute to most external objects, Professor Lloyd Morgan, in the able discussion of this matter in his Animal Life and Intelligence (p. 3 12), proposes to use the term construct for the external object. For our present purpose, it is very needful to bear in mind that an external object is in general a construct — that is, a combination of immediate with past or stored sense-impressions. The reality of a thing depends upon the possibility of its occurring in whole or part as a group of immediate sense-impressions.^ 1 The division between the real and unreal, and again between the real and ideal, is less distinct than many may think. For example, the planet Neptune passed from the ideal to the real, but the atom is still ideal. The ideal passes into the real when its perceptual equivalent is found, but the unreal can never become real. Thus the concepts of the metaphysicians, Kant's thiiio- in itself ox Clifford's iniiid stuff, are in my sense of the words unreal (not ideal), they cannot become immediate sense-impressions, but the physical hypotheses as to the nature of matter are ideal (not unreal), for they do not lie absolutely outside the field of possible sense-impressions. 42 THE GRAMMAR OF SCIENCE S 2. — Sense-Impressions and Consciousness This conception of reality as based upon sense- impressions requires careful consideration and some reser- vations and modifications. Let us examine a little more closely what we are to understand by the word sense- impression. In turning round quickly in my chair, I knock my knee against a sharp edge of the table. Without any thought of what I am doing my hand moves down and rubs the bruised part, or the knee may cause me so much discomfort that I get up, think of what I shall do, and settle to apply some arnica. Now the two actions on my part appear of totally different character — at least on first examination. In both cases physiologists tells us that as a primary stage a message is carried from the affected part by what is termed a sensory nerve to the brain. The manner in which this nerve conveys its message is without doubt physical, although its exact modus operandi is still unknown. At the brain what we term the sense-impression is formed, and there most probably some physical change takes place which remains with a greater or less degree of persistence in the case of those stored sense-impressions which we term memories. Everything up to the receipt of the sense-impression by the brain is what we are accustomed to term physical or mechanical, it is a legitimate inference to suppose that what from the psychical aspect we term memory has also a physical side, that the brain takes for every memory a permanent physical impress, whether by change in the molecular constitution or in the elementary motions of the brain-substance, and that such physical impress is the source of our stored sense-impression.^ These physical im- presses play an important part in the manner in which future sense-impressions of a like character are received. If these immediate sense-impressions be of sufficient strength, or amplitude as we might perhaps venture to say, 1 The closest physical analogies to the "permanent impresses" termed memory are the set and after-strain of the elastician. To assert that they are more than analogies would be to usurp the function of the physiologist. THE FACTS OF SCIENCE 43 they will call into some sort of activity a number of physical impresses due to past sense-impressions allied, or, to use a more suggestive word, attuned to the immediate sense -impression. The immediate sense -impression is conditioned by the physical impresses of the past, and the general result is that complex of present and stored sense- impressions which we have termed a " construct." Besides the sensory nerves which convey the messages to the brain, there are other nerves which proceed from the brain and control the muscles, termed motor nerves. Through these motor nerves a message is sent to my hand bidding it rub my bruised knee. This message may be sent immediately or after my fingers have been dipped in arnica. In the latter case a very coi;nplex process has been gone through. I have realised that the sense- impression corresponds to a bruised knee, that arnica is good for a bruise, that a bottle of arnica is to be found in a certain cupboard, and so forth. Clearly the sense- impression has been conditioned by a number of past impresses before the motor nerve of the arm is called into play to rub the knee. The process is described as think- ing, and as a variety of past experiences may come into play, the ultimate message to the motor nerves appears to us voluntary, and we call it an act of will, however much it is really conditioned by the stored sense-impressions of the past. On the other hand, when, without apparently exciting any past sense-impressions, the message from the sensory nerve no sooner reaches the brain than a command is sent along the motor nerve for the hand to rub the knee, I am said to act involuntarily, from instinct or habit. The whole process may be so rapid, I may be so absorbed in my work, that I never realised the message from the sensory nerve at all. I do not even say to myself, " I have knocked my knee and rubbed it." Only a spectator, perhaps, has been conscious of the whole process of knee- knocking and rubbing. Now this is in many respects an important result. I can receive a sense-impression without recognising it, or a sense-impression does not involve consciousness. In this case there is no exciting of a group 44 THE GRAMMAR OF SCIENCE of stored sense-impressions, no chain of what we term thoughts intervening between the immediate sense- impression and the message to the motor nerve. Thus what we term consciousness is largely, if not wholly, due to the stock of stored impresses, and to the manner in which these condition the messages given to the motor nerves when a sensory nerve has conveyed a message to the brain. The measure of consciousness will thus largely depend on (i) the extent and variety of past sense-impres- sions, and (2) the degree to which the brain can perma- nently preserve the impress of these sense-impressions, or what might be termed the complexity and plasticity of the brain. ^ 3. — The Brain as a Central Telephone Exchange The view of brain activity here discussed may perhaps be elucidated by comparing the brain to the central office of a telephone exchange, from which wires radiate to the subscribers A, B, C, D, E, F, etc., who are senders, and to W, X, Y, Z, etc., who are receivers of messages. A, having notified to the company that he never intends to correspond with anybody but W, his wire is joined to W's, and the clerk remains unconscious of the arrival of the message from A and its despatch to W, although it passes through his office.^ There is indeed no call-bell. This corresponds to an instinctive exertion following uncon- sciously on a sense-impression. Next the clerk finds by experience that B invariably desires to correspond with X, and consequently whenever he hears B's call-bell he links him mechanically to X, without stopping for a moment his perusal of Tit-Bits. This corresponds to a habitual exertion following unconsciously on a sense- impression. Lastly, C, D, E, and F may set their bells ringing for a variety of purposes ; the clerk has in each 1 If these wires were connected outside the office, we should have an analogy to certain possibilities of reflex action, which arise from sensory and motor nerves being linked before reaching the brain — e.g. a frog's leg will be moved so as to rub an irritated point on its back even after the removal of the brain. THE FACTS OF SCIENCE 45 case to answer their demands, but this may require him to listen to the special communications of these subscribers, to examine his lists, his post-office directory, or any other source of information stored in his office. Finally, he shunts their wires so as to bring them in circuit with those of Y and Z, which seem to best suit the nature of the demands. This corresponds to an exertion following consciously on the receipt of a sense-impression. In all cases the activity of the exchange arises from the receipt of a message from one of a possibly great but still finite number of senders. A, B, C, D, etc. ; the originality of the clerk is confined to immediately following their behests or to satisfying their demands to the best of his ability by the information stored in his office. The analogy, of course, must not be pressed too far — in particular, senders and receivers must be considered distinct, for sensory and motor nerves do not appear to interchange functions. But the conception of the brain as a central exchange certainly casts considerable light not only on the action of sensory and motor nerves, but also on thought and consciousness. Without sense -impressions there would be nothing to store ; without the faculty of receiving permanent impress, without memory, there would be no possibility of thought ; and without this thought, this period of hesitation between sense-impression and exertion, there would be no consciousness. When an exertion follows immediately on a sense-impression we speak of the exertion as involuntary, our action as subject to the mechanical control of the " external object " to which we attribute the sense-impression. On the other hand, when the exertion is conditioned by stored sense-impresses we term our action voluntary. We speak of it as determined from " within ourselves," and assert the " freedom of our will." In the former case the exertion is conditioned solely by the immediate sense-impression ; in the latter it is conditioned by a complex of impressions partly im- mediate and partly stored. The past training, the past history and experience which mould character and de- termine the will, are really based on sense-impressions 46 THE GRAMMAR OF SCIENCE received at one time or another, and hence we may say- that exertion, whether immediate or deferred, is to a large extent the product, directly or indirectly, of sense- impressions. ^ 4. — The Nature of TJiougJit There are still one or two points to be noted here. In the first place, the immediate sense -impression is to be looked upon as the spark which kindles thought, which brings into play the still remaining impresses of past sense-impressions. But the complexity of the human brain is such, its stored sense -impressions are linked together in so many and diverse ways — partly by continual thinking, partly by immediate sense-impressions occurring in proximity and so linking together apparently discordant groups of past impressions — that we are not always able to recognise the relation between an immediate sense- impression and the resulting train of thought. Nor, on the other hand, can \ye always trace back a train of thought to the immediate sense-impression from which it started. Yet we may take it for certain that elements of thought are ultimately the permanent impresses of past sense -impressions, and that thought itself is started by immediate sense-impressions.^ This statement must not be in any way supposed to narrow the material of thought to those combinations of " external objects " which we associate with immediate sense-impressions. Thought once excited, the mind passes with wonderful activity from one stored impression to another, it classifies these impressions, analyses or simplifies their characteristics, and forms general notions of properties and modes. It proceeds from the direct — what might perhaps be termed the physical — association of memory, to the indirect or mental association ; it passes from 1 The exact train of thought which follows an immediate sense-impression depends largely on the physical condition of the brain at the time of its receipt, and is further largely conditioned by the mode in which stored sense- impressions have been previously excited, i.e. the extent to which memory has been exercised in the past. THE FACTS OF SCIENCE 47 perceiving to conceiving. The mental association or recognition of relation between the impresses of past sense-impressions has probably, if we could follow it, as definite a physical side as the physical association of im- mediate sense-impressions with past impresses. But the physical side of the impress is only a reasonable inference from the physical nature of the immediate sense-impression, and we must therefore content ourselves at present by considering it highly probable that every process of thought has a physical aspect, even if we are very far as yet from being able to trace it out. This process of mental association we can only recognise as certainly occurring in our individual selves. The reason why we infer it in others we shall consider later. The amount of it, however, in our individual selves must largely depend on the variety and extent of our store of impresses, and further on the individual capacity for thinking, or on the form and development of the physical organ wherein the process of thinking takes place, i.e. on the brain. The brain in the individual man is probably considerably influenced by heredity, by health, by exercise, and by other factors, but speaking generally the physical instruments of thought in two normal human beings are machines of the same type, varying indeed in efficiency, but not in kind or function. For the same two normal human beings the organs of sense are also machines of the same type and thus within limits only capable of conveying the same sense - impressions to the brain. Herein consists the similarity of the universe for all normal human beings. The same type of physical organ receives the same sense-impressions and forms the same " constructs." Two normal perceptive faculties construct practically the same universe. Were this not true, the results of thinking in one mind would have no validity for a second mind. The universal validity of science depends upon the similarity of the perceptive and reasoning faculties in normal civilised men. The above discussion of the nature of thought is of course incomplete ; it offers no real explanation of the 48 THE GRAMMAR OF SCIENCE psychical side of thought. It is merely intended to suggest the manner in which we may consider thought to be associated with its physical accompaniments. What the actual relations between the psychical and physical aspects of thought are, we do not know, and, as in all such cases, it is best to directly confess our ignorance. It is no use, indeed only dangerous, in the present state of our know- ledge with regard to psychology and the physics of the brain, to fill the void of ignorance by hypotheses which can neither be proven nor refuted. Thus if we say that thought and motion are the same thing seen from different sides, we make no real progress in our analysis for we can form no conception whatever as to what the nature in itself of this thing may be. Indeed, if we go further and compare thought and motion to the concave and convex sides of the same surface, we may do positive harm rather than good ; for convexity and concavity when accurately defined by the mathematician are not different qualities, but only degrees of the same quantity, curvature, passing the one into the other through zero-curvature or flatness. On the other hand, the distinction between the psychical and physical aspects of brain activity seems to be essen- tially one of quality, not of degree. It is better to content ourselves in the present state of our knowledge by remarking that in all probability sense-impressions lead to certain physical (including under this term possible chemical) activities of the brain, and that these activities are recognised by each individual for himself only under the form of thought. Each individual recognises his own consciousness, perceives that the interval between sensa- tion and exertion is occupied by a certain psychical process. We recognise consciousness in our individual selves, we assume it to exist in others. ^ 5. — Other-Consciousness as an Eject The assumption just referred to is by no means of the same nature as that which we make every moment in the formation of what we have termed constructs from THE FACTS OF SCIENCE 49 a limited group of immediate sense-impressions. I see the shape, size, and colour of the blackboard, and I assume that I shall find it hard and heavy. But here the assumed properties are capable of being put to the direct test of immediate sense-impression. I can touch and lift the blackboard and complete my analysis of its properties. Even the Capitol in Washington, of which I have had no direct sense-impression, is capable of being put to the same sort of direct test. Another man's consciousness, however, can never, it is said, be directly perceived by sense-impression, I can only mfer its existence from the apparent similarity of our nervous systems, from observing the same hesitation in his case as in my own between sense -impression and exertion, and from the similarity between his activities and my own. The inference is really not so great as the metaphysicians would wish us to believe. It is an inference ultimately based on the physical fact of the interval between sense-impression and exertion ; and though we cannot as yet physically demonstrate another person's consciousness, neither can we demonstrate physically that earth-grown apples would fall at the surface of the planet of a fixed star, nor that atoms really are component parts in the structure of matter. It may be suggested that if our organs of sense were finer, or our means of locomotion more complete, we might be able to see atoms or to carry earth-grown apples to a fixed star — in other words, to test physically, or by immediate sense-impression, these inferences. But : — " When I come to the conclusion that you are conscious, and that there are objects in your consciousness similar to those in mine, I am not inferring any actual or possible feelings of my own, but your feelings, which are not, and cannot by any possibility become, objects in my con- sciousness." ^ To this it may be replied, that, were our physiological knowledge and surgical manipulation sufficiently complete, it is conceivable that it would be possible for me to lae 1 W. K. Clifford, "On the Nature of Things-in-Themselves," Z-et/?ie reason may be at work in two quite distinct fields. It is important to notice, however, that in one sense civil and moral laws are natural pro- ducts ; they are products of particular phases of human growth. This growth is itself capable of treatment by the scientific method, and the sequence of its stages can be expressed by scientific formulae, or — looking at civil and moral law as objective phenomena — by natural laws. Thus civil law is a natural product, and not 1 Up to the " sameness of the reason " there is little exception to be taken to the argument, but few of us would agree with the dictum of that ancient and upright judge, Sir John Powell, that " nothing is law that is not reason." 94 THE GRAMMAR OF SCIENCE identical with natural law — any more than the particular configuration of the planetary system at this moment is identical with the law of gravitation. We are now, I think, in a position to draw a clear distinction between civil (or moral) law and natural law. Civil law takes its origin in natural law in the old sense (p. 88), while its growth and variation can, in broad outline at least, be described in the brief formulae of science, or in natural laws in the scientific sense. Civil and moral laws are the natural product of societies, and of classes within society, struggling in the early days for self-preservation, and in these later days for a maximum of individual and class comfort. A civil law, according to Austin, is a rule laid down for the guidance of an intelligent being by an intelligent being having power over him. Such a rule varies with every age and every society. On the other hand, a natural law is not laid down by one intelligent being for another ; it involves no command or corresponding duty, and it is valid for all normal human beings. It has taken centuries for men to arrive at a full appreciation of this distinction, and it would be well could the distinction be now em- phasised by the specialisation of the word law in one or other of its senses. We sadly need separate terms for the routine of sense-impressions, for the brief description or formula of science, and for the canon of social conduct, or, in other words, for the perceptive order, the descriptive order, and the prescriptive order. Historically we cannot say that any of these orders has the higher claim to the title law, for the Roman ideas of law must at least be traced back to their Greek parentage. Here, in the Greek word v6[jbo