This was the conception which Bacon had shadowed out, which Leibniz had presented under many names and with many applications, as the olive-branch between Plato and Democritus; it now became through philosophical and extra-philosophic acceptance a current maxim in the general field of knowledge. Nature assimilated to history, and history assimilated to nature: freedom built upon necessity, and efficient causes rounded off, though not entirely merged, in final. It is the recognition of law, order, causality in the psychical world, yet not of mere so-called natural law; and therefore without reducing it to a merely physical and material world. It is in fact the new method which is inevitable and necessary, as soon as it is manifest that life, organisation, development is the underlying truth and central notion of things. You look at the world at first, let us say, as a mere collection of separate things in varying degrees of juxtaposition: and all that you think of doing to them, either by way of theory or practice, is to put them together, to link them closer, or separate them more widely. You do so from outside by an arranging force; for they are assumed to be purely passive, waiting to be touched, each set in its place—from which it can only be moved by a push or a pull. This is the method of mathematics or mechanics. It shows the dexterity of the agent or of the expositor: but you feel that it is artificial, and arbitrary. It is analytic or synthetic—but not auto-analysis or auto-synthesis. The director of the movement (we may call it 'construction') may no doubt have the real secret: he may work the things well and fairly, and unite or divide them according to inner affinities; but we cannot, as matters stand, be sure of this. The things, in fact, he deals with have been already emptied of all life and peculiarity of their own: they are alike in quality, only differing by a more or less,—a difference which at any moment may be altered by an act of subtraction or addition. No doubt you can build up what are called systems—compounds of a kind—in this way: but they do not really hang and grow together; they are only prevented from breaking up by the absence of any empty place to which the parts may withdraw. Bit holds up bit; but how all the bits have found themselves so caged up without exit is a mystery. Absolute neutrality or indifference of each part to others, and yet absolute equilibrium[1] in the total composite,—such is the situation.
The chemical method (taking chemistry as a type of the sciences like optics, electricity, &c.) is a revelation of a different state of affairs. The elements of things are here seen to be unique and incomparable; yet in each there is a latent sympathy ready to break out when the proper occasion arrives. Bring two things together, and their affinity suddenly, in the proper circumstances, leads to their complete fusion: a product arises which, when formed, hardly betrays its origin and composition. In a way this is the converse of the mechanical or mathematical method. In it was no fusion, no inner mixture: each part after composition lay beside the other, and their union was only in the ideas of the onlooker. It was mere juxtaposition still,—though now closer: an abnormally keen eye would still have been able to descry the dividing lines and measure the gaps. At least mere mechanical physics tends so to conceive it. Here, on the contrary, there is union—but only at the moment of fusion: once that is accomplished, the result is apparently simple, and bears no suggestion of being a compound. In the mechanical union the result is exactly equal to the sum of the elements which go to make it: in the chemical there is something positively new, something, i. e., of which the premises gave no indication and made no promise.
Either of these methods,—of these conceptions of existence—works well in a certain region. But both of them only do their work on a certain hypothesis, or with a certain abstraction. The mechanical method supposes that objects are all qualitatively alike, differing only in quantity or weight: all therefore entirely comparable with each other, and capable of being substituted for each other in an equation. Where this assumption holds good, the method of addition and division, the method of the calculus does its work[2]. The chemical method works on another assumption,—the assumption of a number of qualitatively-differenced elements, of elements which also are, so to speak, set on edge against some, and ready to leap into the arms of others. If the observer in the first case had the game entirely in his own hand,—could build up and separate at his pleasure, could determine results a priori: he is here baffled by the unexpected, and can only wait and watch to learn a posteriori the behaviour of the bodies possessed of this occult and non-predictable affinity. At the best he can only formulate what he observes, try to classify it, ascertain any common principles running through it, any serial recurrences, or the like: and that is all that chemical philosophy can achieve. Chemical affinity—the fact that certain elements combine in certain ways, and refuse to enter into certain alliances—is a great fact: but to a priori reasoning or abstract syllogising it is an entire inexplicability, one of the accidents in the universe which must be reckoned with, but cannot be understood.
It is probably evident that, if we want to get a comprehension of the life and concrete reality of things, neither of these methods will quite answer the purpose. With the first alone, if it could be universally carried out, the universe would be thoroughly explained: everything would be exactly equivalent to some sum or multiple of every other: there would be no mystery, nothing unique, and strictly individual. Given time, we could find a formula for every reality, and a predicate exactly fitted to any subject. Yet even mathematics has to confess the existence of irrationals, surds, infinite series, and the like. For our unities and standards are always arbitrary, artificial, and one-sided, and fall short of the subtlety of nature. Even our simpler types of surfaces—the circle and the square—remain irreducible to each other: and we only avoid the collision by the remark that practically and with any required amount of exactness the discrepancy between the two can be adjusted. If we turn to the chemical method, again, there is a nearer approach to actuality in the recognition of the presence of something more than mere composition and juxtaposition. It is not that there is something which is not juxtaposition: but rather it is much more than mere juxtaposition. There may be degrees of this something more: but it is only to a gross or abstract view that it is not present at all. Mere cohesion even shows a unity in things juxta-posed. Mere contact is contagious: it infects. 'When a violin has been played on frequently by a tyro,' says G. H. Lewes, 'its tone deteriorates, its molecules become re-arranged, so that one mode of vibration is more ready than another[3].' 'Toute impression,' he quotes from Delboeuf, 'laisse une certaine trace ineffaçable.' So-called chemical composition is only a conspicuous instance, with peculiarities, of this alteration in state produced by what, from the mechanical standpoint, are called inner molecular displacements. But to recognise a fact is one thing: to give its explanation is another. Yet, on the other hand, to recognise the fact is to note an important point which had been omitted by the mechanical construction of things. There the result could hardly be called new: it was exactly equal to its constituent elements: and the equation was transparent. And it was transparent because the whole process, analysis and synthesis, was not a work or process of the observed thing, but the work of the observing mind: it makes the (artificial) unities, numbers them, and adds them or subtracts. But with the chemical result, though it also is equal to its elements, there is something new. Water, no doubt, is oxygen and hydrogen, but here, at least, there is no doubt that the plus sign unduly simplifies the relationship, and rather indicates or represents a nexus than accurately defines it. And yet, there is nothing in water which was not, in some—shall we say mysterious?—way, in the oxygen and the hydrogen. Chemical physics, therefore, brings out clearly, or comparatively clearly, something which the ordinary and coarser simplicity-loving theory is obliged and is able to neglect: it realises the virtue that lies in juxtaposition, and shows that the mere outer change of quantity goes with a deeper inward and qualitative one. The result does more than sum up and condense what was spread out in extension and dispersed in parts before: it brings out or reveals something which previously was unsurmised. Always, in a liberal interpretation of the maxim, it is true that Ex nihilo nihil fit: but here, especially, the effect actually discloses what was—but was latent or unperceived—in the premises. The maxim, to be fairly treated, must be read backwards as well as forwards.
But we must go a step further if we wish the full explanation. If the premises are to be adequate to support the conclusion, they must be restated in terms which hint at the conclusion—which in a way contain it, but contain it in potentiality and promise, not in act. This is the method of development, which is the method that is applicable to full concrete reality, not like the others to parts abstracted from or insulated in reality. So long as you deal with these selected bits of fact—abstracted from their surroundings, subject to strict observation or strict experiment, you can apply a comparatively simple and straightforward method. You are dealing with abstracted, mutilated, prepared fact. You are guided in these cases by the canons of identity and difference: you add and subtract, or subtract and add; and that is all. You use what are called the rules of experimental method. But these canons do not directly apply—except by happy accident—to the real world, where antecedent and consequents are not separate and tabulated, as the logical canons, the rules of formal logic, require. In dealing with this concrete reality, a much more complex method is needed, a method which has to blend induction with deduction, and to start from both ends in the series of causation at once. You can apply observation or experiment, only when the issues have already been extremely simplified and narrowed down: when the question has been rendered so definite that it is next-door to the answer, and the removal of a slight partition-wall will as it were make the two one clear space. Where observation and experiment are available, indeed, is where the general outlines and principles of the subject are settled, where the scheme of reality is defined in large, but a variety of minor issues still remains to be settled. Unless this general framework is fixed, neither observation nor experiment, with their canon of identity and difference, are of any avail. These methods, therefore, only apply in sciences which are in principle or substantially complete, though admitting of possibly infinite extension in details and particulars. Where the science is yet to constitute, i. e. in dealing with the kinds of real things in their completeness, and not as viewed in some definite aspect, induction and deduction must go hand in hand and help each other at every step: and if they, as they must, have recourse to experiment and observation, it will be at first in a very unsatisfactory and tentative way.
Such is the way the contrast between the simplicity belonging to an artificial method dealing with picked instances, and the complexity that real concrete organic nature demands, presented itself to J. S. Mill as he advanced in his inquiry. The only complete method for the investigation of unsophisticated nature, not yet mapped out and defined in general departments, is the deductive-inductive method in which induction and deduction separately have a subordinate place,—using induction in the narrow sense the term has been hitherto allowed to bear. And that sense, it may be added, is, as in some passages of Aristotle, little else than a reverse of syllogism, or to speak more accurately, it is a syllogism which goes up to generals instead of descending from them. It is like the syllogistic deduction formal and abstract in character. The (deductive) syllogism assumes the existence of major premises—of general propositions which in the last resort, if they are real bases, must be primary and true, or self-evident facts. But a critic, like Mill, had little difficulty in showing that a general truth rests upon and presupposes the very particular conclusions which it is used to establish. Unless every singular is true, the universal which embraces or unifies them cannot really be true. Therefore the conclusion is really implied and presupposed in the principles of its premises. But, unfortunately for the application and supposed sequel of this not unjust remark, a similar remark may be made on the ordinary exposition of the inductive method. Induction, it is said, infers from or on a basis of single facts. But if a single truth is really, i. e. unconditionally true, it is indistinguishable from the universal. If it is really true once, it is true for ever. The assertion of the individual proposition as true, if it can be supported—(and unless it be true, what basis can it afford for the general conclusion?)—implies the truth of the universal it is sometimes used to establish. The inductive logician tells us to build on singular and definite facts, on truths of definite and individual experience: but a definite or determinate truth rests upon universality (indeed is a universal), and cannot be found unless we have already found the special total or organism of truth in which it forms a part. Individuals and universals presuppose each other, and do not, as the first impression leads us to think, stand apart as two unconnected termini, from either of which, if we happen to be so located, we can without road or railway make a legitimate passage to the other.
If it be urged, as it may naturally be, that on this showing there is no solid or 'absolute' starting-point at all, the contention may be conceded. The only fixed and steady points in knowledge are points hypothetically fixed,—certified, that is, for the time and in the circumstances we employ them. But in the open field—or rather in the wilderness—of knowledge, where the ground of fact is not staked off, and the unexpected may always turn up, the only test of truth is the corroboration given by the consilience of paths initiated from different points: it is only by an undesigned coincidence in the results of independent operations that you can succeed in orienting yourself. You begin your road at two ends, and you meet: you locate or fix your point by drawing its co-ordinates to two direction-lines taken anyhow at first, and only in formed science diverging at a fixed angle. And in the absolute your direction-lines cannot be supposed fixed: you can only gradually adjust them to each other as you proceed. Intelligence, says Aristotle, is a principle, a beginning; and intelligence, he says again, supplies beginnings[4]. Science, in the technical sense, only comes into operation,—or, in other words, deduction and (in the narrower sense used by Mill, and proceeding by pure observation and experiment) induction only find a way,—where beginnings and principles have been set up, where an approximate order or provisional system has been established. And if logic, in its stricter sense, is the method of sciences already made and in their essentials constituted, then logic can be asked to do no more than to provide a theory of such formal processes. If it traces the path which leads 'from the known to the unknown,' if it always proceeds on the hypothesis of a given knowledge, then such induction or deduction (from certain and approved singular facts, or from certain and approved general truths) fully satisfies the practical need of the scientific reasoner. But if Logic be, as it sometimes is, and may very reasonably be, taken in the wider sense of an epistemology,—a theory of the nature and origin of knowledge as a whole, and not of mere inference or syllogism;—if it does not merely ask how we can satisfactorily get from one piece of knowledge (we are supposed to have) to another (not yet supposed to be), but how we come to have knowledge at all; then its problem must go behind the rudiments of vulgar induction and deduction. It must ask—what, so far as one can see, Mill and his mere followers have never seriously asked at all—what induction is, what are its relations with deduction, and what is the place of either in the process of knowledge. And as the process of knowledge is the path to reality, it must also ask about the nature of this goal,—reality and truth. It is all very well for the narrower Logic to formulate in terms the methods actually employed in sciences: to state in abstract canons what is there seen in life and action. But a Science of Logic—an epistemology—(and a genuine epistemology cannot claim to be anything short of an ontology) must face the fact of science itself—must ask how the ideas of the knower must—or otherwise they are not knowledge—embrace and contain the reality of the known. The other and narrower Logic is and will remain a theory of forms of reasoning-a transcript in fainter terms of the procedure of science in any given step it takes upward to generals or downward to particulars: but the logic which deals with knowledge as such, in its systematic entirety,—the transcendental Logic, in short, must have a real value, an invincible relation to reality. The formal Logic—the logic of Mill and Hamilton—must be carried back to its principles, to its first step: and that first step which will also be the last step, and the inspiring principle of every intermediate step, is that of Intelligence (Aristotle's Νοῡς), of which the products or manifestations are λόγοι, i. e. definite conceptions, categories, formulations of rules and principles of definite range,—determinations or special types of unity.
Mill really faced the problem of method to better effect when he came to deal with a class of questions in which he was really interested, and which moreover have for epistemological purposes the advantage of being as yet unreduced into the rank and file of disciplined science. These questions are those dealing with man, his mental and moral nature, and history. Even its advocates or patrons occasionally admit that there is no accepted idea of what Sociology is or does. Its name at least expresses a longing towards a unity, or a presentiment that there is some underlying unity and common method in the group of what are loosely called the moral, or the historical, or the social and political sciences. But sociology is, as most people will allow, the name of a science unrealised—the felt and consciously-apprehended need of a science, and the dissatisfaction with the existing state of knowledge in certain departments. And undoubtedly it was with problems of social science,—problems of politico-economic and socio-ethical or socio-religious matters, that Mill's interests were mainly engaged. Like his master in this department, Auguste Comte, he wanted to carry into the topics which he was chiefly bent upon that 'scientific' precision which they by pretty general admission lacked, and which revolutionary movements had shown they greatly needed. But he could not help seeing that the 'induction' of dynamics and physics was not exactly the instrument he was in search of. Theory and hypothesis here demanded a much larger share in the process than in the more mathematical sciences. Causes and effects in reality here rolled round into each other, instead of remaining calmly fixed, one set here, and the other there. Of course even here—i. e. in organic and concrete sciences—it is possible to introduce observation and experiment,—no doubt, with greater effort and constraint, but still not altogether impracticable. But the artificial and mutilative character of such experimentation is felt here in a way different from its pressure in other cases. And what is more important, to institute an experiment or set on foot a scientific observation (and to observe means to watch a definitely restricted natural process with a view to answer some question about it), presupposes—as we have already seen—a tolerably definite provisional theory as to the general lie of the country to be investigated. Only when the country has been reasonably well mapped out in provinces and provided with some system of roads, can these problems of detail—questions to be answered Yes or No—be profitably put. And it is—in some parts of the historical sciences at least—somewhat premature to put questions requiring a categorical reply. There is only the vague malaise of felt difficulty to guide us. We do not, in many cases, know what it is that we want to know; for, it demands a good deal of wisdom and trained art to put the proper or reasonable question,—so much so, indeed, that to succeed in formulating your question fully is equivalent or nearly equivalent to being able to answer it. The value of observations and experiments—which are ways of putting nature to the question and it may be to the torture—depends entirely upon the knowledge and the command of general ideas possessed by the observer and experimenter. And the same may be said of the reduced and tabulated conspectuses of the results of many observations and experiments which are called Statistics. Their value depends on the truth and breadth of view which presided at their collection and arrangement[5].
The historical or genetic method is the method of Science in general, but considered and employed under a limited aspect. And under its more comprehensive aspect it may be called—though no name is unimpeachable—the method of development. Now the essence of the idea of development—as was clearly shown by Leibniz—is the refusal to admit external interference, and the resolve to let a thing explain itself by itself. It does not, like the mechanical method, manipulate the thing from outside—try to add it up out of factors or items fashioned and fabricated after some external standard. Nor does it, like the chemical, look at the result as an inexplicable alteration, due apparently to a mere stroke of combination or disintegration—yet not obviously reducible to a mere equivalent of its elements. On the contrary, it recognises in the object a certain independence or originality, yet also the presence of an immanent law which does not wait for the outsider to put it together, but constructs itself, as it were, after a plan of its own. There is in the so-called object, though we do not at first sight recognise it, the same originative principle both analytic and synthetic, as we own in thought. The object is—in a true logic—a process, a self-completing process, and not merely an object, mechanical, or other object. It changes, grows or decays, while we observe, unless for brief instants we cut it off from its connexions and arrest its development. And our observation, if truly scientific, must be sympathetic with its process of change. It is neither a mere thing to be explained and construed ab extra: nor a mystery of sudden transformation to be passively accepted; but a growth, a history, to be sympathetically watched and understood,—understood, because it follows the same order as the movement of our own thought in the process of knowledge. Similia similibus cognoscuntur[6].