[8] _First Principles_, -- 46.

[9] MILL, _Inductive Logic_, bk. iii. ch. xii. p. 549.

[10] _Ibid._

[11] _First Principles_, ch. iii. -- 46.

[12] SETH, _Chambers's Encyclopaedia_, _s.v._ "Philosophy."

[13] KIRCHOFF, _Vorlesungen uber mathematische Physik_, i. p. 1.

[14] MERTZ, _History of European Thought in the Nineteenth Century_, i. pp. 382, 3, note.

[15] LOTZE, _Microcosmus_, E. T., ii. p. 718.

[16] LOTZE, _Microcosmus_, E. T., ii. p. 718.

[17] MILL, _Inductive Logic_, bk. iii. ch. vi.

[18] MILL, _Inductive Logic_, bk. iii. ch. vi.

[19] CLAUDE BERNARD, quoted in _L'Annee Sociologique, premiere annee_.

[20] _Principles of Biology_, v. -- 30.

[21] _Principles of Sociology_, vol. i. part ii.

[22] _Ibid._, -- 260.

[23] _First Principles_, -- 127.

[24] _Ibid._, -- 153.

VII.

NECESSITY

We have seen that if material things can alone be treated of by science, if things which can be seen and handled are alone amenable to the methods of science, then there can be no science of mind, and no scientific laws to regulate mental phenomena. In the same way, if the field of evolution is completely filled by the redistribution of matter and motion, then there is no room left in the theory of evolution in which to accommodate the history of ideas or of morals, there is no evolution of thought or morality, no continuity between higher and lower in the intellectual development of man and the brute.

We may admit that the methods of mental and moral science, of sociology and political economy, are not identical with those employed by physics or chemistry or astronomy. But we cannot admit that the facts which, if not the proper study of mankind, are at any rate of the greatest interest to man, are not subject to or part of the process of evolution, and cannot be reduced to scientific law and order. The methods of the philosophical sciences may not be the same as those of the exact sciences; but neither are the methods of chemistry those of astronomy--just as the instruments of the astronomer are not those of the chemist. The exactness which is attained by those sciences that can apply the methods of mathematics to their subject-matter cannot be rivalled by philology or psychology. But it is not to all the material sciences that the mathematical methods can be applied: meteorology deals with matter in motion, but not yet with exact.i.tude. The intangible and invisible, but none the less real, facts of our mental and moral experience can be measured to some extent by the statistics and averages and curves employed by the sociologist, the demographer, and political economist: the intensity of a desire may be estimated roughly and relatively by the "effective demand" for its object, the will to live by the number of suicides.

Again, we may admit that the laws of the exact or material sciences do not extend to mental science, without thereby forfeiting the right to subject mental phenomena to scientific investigation and a.n.a.lysis.

Chemistry does not cease to be a science because chemical affinity cannot be exhibited as a case of the gravitation formula. Need psychology renounce the claim to be a science because the laws of the a.s.sociation of ideas cannot be deduced, say, from the laws of motion?

Of course, if science has no other object than to describe with mathematical accuracy the exact way in which material things move, if no method is scientific which does not result in such a formula, and if no generalisation, however true, is scientific which does not formulate motion in s.p.a.ce, then, indeed, it is unscientific to talk of the evolution of mind and thought, of man and of society.

On the other hand, the movements of material things in s.p.a.ce are facts of which we are aware, phenomena of which we are aware through our senses; in a word, they are sense-phenomena. We are aware of them as existing simultaneously and in combination, or as succeeding one upon another; and no truth, even of the most mathematical and exact of the sciences, does, or can do, more than express with mathematical exactness the precise conditions under which these sense-phenomena co-exist or follow one another, or the precise conditions without which such co-existence or sequence cannot take place. A mathematical science dealing with material things states only and always that certain sense-phenomena occur invariably and uniformly under certain conditions.

The exact sciences move within the limits of the Uniformity of Nature and the law of Universal Causation; and their subject-matter consists of sense-phenomena, _i.e._ of things which, as known to science, are objects of perception to some mind.

But sense-phenomena are not the only mental phenomena of which we are aware: there are ideas which we do not see or handle, or smell or taste, but of which we are nevertheless distinctly conscious. Thought has its movement, ideas have their co-existence and sequences, the a.s.sociation of ideas has its laws. There is a uniformity of human nature as well as of external nature; there are conditions under which certain actions are always performed, and without which they would never be done. Whether the body of propositions in which these conditions are formulated be accorded or denied the name of science, matters little. But it is difficult to see what are the so great differences between these phenomena and sense-phenomena that make the latter amenable and the former insusceptible to scientific treatment. Is it that ideas are invisible? So is weight, yet the gravitation formula is scientific. Is it that thought is impalpable? So is colour, so is sound--yet there are optics and acoustics.

Be this as it may, what makes things material susceptible to scientific treatment is a quality which is not peculiar to them, but which is shared by them in common with things immaterial: it is that they are objects of which the mind is immediately aware, phenomena present to some consciousness, and that they are phenomena which appear in consciousness as co-existent and successive in certain definite uniform modes which can be detected by thought and formulated in general propositions, or laws.

If the theory of evolution comprehends all things, mind and morals as well as matter and motion; if the law of continuity connects all things together, immaterial as well as material, in a process which moves without break or interruption; it is because all things agree in the fact that they are presented (whether in sense or in idea) to the mind, and because they are presented in the continuity of consciousness.

But the object of the scientific mind is not to observe and record all the phenomena presented to it in the continuity of consciousness. On the contrary, it neglects and rejects many; but always with a purpose, viz.

that of ascertaining and describing, as precisely as possible, the conditions under which a given co-existence or sequence occurs (and therefore may be expected to recur) and without which it fails to occur.

In other words, science a.s.sumes that everything has a cause, and that in accordance with the uniformity of nature what has happened once will happen again in the same circ.u.mstances; that a cause will, in the absence of counteracting causes, produce its effect. Without these a.s.sumptions science cannot treat of any subject: no department of knowledge can be dealt with scientifically if these a.s.sumptions are not admitted with regard to that department. On the other hand, if by the aid of these a.s.sumptions we are enabled to reduce any set of phenomena to law and order, our success is of itself sufficient ground for regarding the a.s.sumptions as warrantable and justifiable. For science, at any rate, the only question is whether as a matter of fact they do enable us to determine under what conditions given co-existences or sequences will ensue, or what conditions such a co-existence or sequence necessarily implies.

With regard to human activity, mental and physical, it is plain matter of fact that such uniformities of sequence and co-existence not only can be but are demonstrated to prevail; and the extension of the scientific principle of cause and effect to the domain of human will and action is scientifically justified. The comparative sciences which deal with man and his works and words--archaeology, anthropology, philology--are perpetually engaged in demonstrating, with fresh proofs every day, the uniformity of human nature: in similar circ.u.mstances men have always behaved in similar ways. To satisfy the same needs, they have manufactured similar instruments at similar stages of development: flint arrow-heads from Mexico or j.a.pan resemble those taken from British barrows; the pottery of early Greece is hard to distinguish from that of Peru; the purpose of many stone implements of unknown antiquity has been discovered by a comparison of the use to which similar tools are put by savages still existing. That man's words, as well as his works, exhibit law, order, and uniformity in their growth, as well as in their phonetic decay, is shown by the science of comparative philology. That in the face of the same problems similar a.n.a.logies have been used to produce similar solutions, is revealed by comparative mythology: the imagination, which might have seemed most free to throw off the trammels of law and of monotonous uniformity, falls in similar circ.u.mstances into very similar grooves.

If the will of man is not revealed in the things which he makes, in the words which he speaks, and the thoughts which he thinks, it is difficult to know where to look for its manifestation. If, on the other hand, it is manifested in these ways, then, whether it be free or not, it is clearly uniform in its action; and the extension to it of the law of causation seems fully justified by the results.

The recognition of the universality of the law of causation must not, however, be supposed to carry with it any implication that there are no differences between, say, the organic and inorganic, or that the laws of the one are identical with or deducible from those of the other; the a.s.sociation of ideas may be a scientific and established fact, and yet not obey the same laws as the adhesiveness of material substances. What unites all things into a continuous, coherent, and systematic cosmos, into a scientific whole, is first the fact that, whether phenomena in sense or phenomena in idea, they are all objects of thought; and next the fact that they all exhibit the universality of causation and the uniformity of nature.

Whether this uniformity which binds man and nature into one consistent whole is a uniformity of will or a uniformity of necessity, is quite another question. It is a metaphysical and not a scientific inquiry; and the metaphysical answer, whatever it may be, is one for which science does not and need not pause. So long as nature is granted to be uniform, it matters not to science whether the uniformity is of necessity or is freely willed. In either case the sequences or co-existences described by science will continue, under the circ.u.mstances described, to happen as described.

It is, however, commonly a.s.sumed that actions which are uniform are, by their very uniformity, proved to be necessitated; and that unless what happens was bound to happen, there can be no uniformity and no science.

Hence on the one hand the recognition of the freedom of the will has been denounced as fatal to all scientific conceptions of human nature; while on the other hand the uniformity of human nature and action has been denied as being inconsistent with the freedom of the will. The one side has pointed to one set of facts, which prove irresistibly that men do will the same thing under the same circ.u.mstances. The other side has pointed to the equally undeniable fact of our consciousness of freedom.

The essential feature in our consciousness of freedom is our conviction that in the present we can do or abstain from doing a contemplated action, and in the past, though we did the thing, we might have abstained from it or have done something else. Now, whether this possibility that what took place might not have taken place is a real one or only a delusion, matters not to science. If real and true, it is indeed fatal to one particular metaphysical theory, viz. that every event which ever occurred was bound to occur and could not have happened otherwise; but it leaves every truth of science, every one of those concise descriptions of what takes place under given circ.u.mstances, absolutely intact. The freedom of the will is anathematised in the name but not in the interests of science.

That becomes clear when we reflect that the laws of science are, and do not pretend to be more than, hypothetical statements. The gravitation formula does not state that bodies do as a matter of fact actually fall at the rate of sixteen feet in the first second, and so on. The statement, if made, would be untrue: a feather floats much more slowly to the ground. Still less does the formula affirm that all bodies move towards each other--and for a very good reason: many bodies are at rest.

The formula makes no definite statement as to what actually does occur: it merely states what would or will happen under certain circ.u.mstances; and it is doubly or trebly hypothetical. First, it a.s.serts conditionally that if, and only if, bodies are free to move, they will tend to move towards each other at the rate of sixteen feet in the first second, and so on. Next, even if this condition be fulfilled in a particular case, and a given body is free to move, say, towards the earth, the law of gravitation does not a.s.sert that the body will absolutely, or unconditionally, or of necessity fall sixteen feet in the first second: it only affirms that the body tends to move at that rate, and the word "tends" conveys in its meaning a second hypothesis. What is meant by saying that a body tends to fall, or tends to move in a straight line, is simply that the body will fall or move in the direction or at the rate mentioned, provided that nothing happens to prevent it. The law of gravitation then, like every other law of science, from the very terms in which it is stated, contains two hypotheses: _if_ bodies are free to move, then they _tend_ to move at a certain rate. Further, like every other law of science, it is based on a third hypothesis, which, as it is a.s.sumed by all scientific laws, is not expressly referred to by any.

That third hypothesis is that nature is uniform: if a body is free to move it will, in the future as in the past, tend to move at a certain rate, provided that nature is uniform.

Now, throughout all this, it is obvious that science knows nothing about "necessity." Indeed, it is obvious that science, by the trebly hypothetical form of all its laws, has taken particular pains to avoid prejudging the question whether what happens was bound to happen. As we have already said, science takes care to frame its statements in such a way that they are quite independent of metaphysical theory, and will remain as true within their limits if the theory of necessity prove erroneous as they will if it turns out to be correct.

Nor can it be said, thus far, that the laws of science lead us to the theory of necessity as their logical conclusion. It may be true that if I walk over a precipice I shall fall to the bottom, in accordance with the law of gravitation. But it does not logically follow that therefore I must walk over. It may be true that a suspension bridge will fall in the same way, if the supports be removed; but it does not follow that they are therefore bound to give way. It may be true that if nature is uniform certain sequences will happen; but it does not therefore follow that nature must be uniform. In other words, the theory of necessity, if true, cannot be based on science, but must rely on some metaphysical considerations. Science does not undertake to prove even that nature is uniform, much less that it is uniform of necessity. The opposite theory, that the uniformity of nature or of human nature is due to the action of a will freely manifesting itself as uniform, may be considered superfluous from the scientific point of view. But the theory of necessity from the same point of view is equally superfluous. As long as events do happen uniformly, science has all she wants--whether their uniformity is of will or of necessity is for her quite a superfluous question. And if science were all that man wanted, these rival metaphysical theories would be of no interest to him either. But the persistency of the attempt to extract some support for the metaphysical theory of necessity out of the facts of science shows that men of science, being men, must have their metaphysics.

Are there, then, other facts of science, or a.s.sumptions essential to science, which require the metaphysical theory of necessity as their presupposition or entail it as their natural consequence? Probably the reply will be that there is one such principle: that of the Universality of the Law of Causation. The a.s.sumption that everything _must_ have a cause may be on the part of science a pure a.s.sumption, and one which, like the Uniformity of Nature, cannot be proved by science; but it does, it may be said, a.s.sume the existence of a necessity in things.

It does, it may be replied, but whether the necessity which science a.s.sumes is the same as that maintained by the metaphysical theory in question, may be doubted. The metaphysical theory is that everything which happens happens of necessity, and could not have happened otherwise than it did. The a.s.sumptions which science makes with regard to causation are that nothing can happen unless the conditions requisite to its production are fulfilled, and that when those conditions are present the result necessarily follows. The question is whether this scientific necessity is the same as that metaphysical necessity; or, if they are not the same, whether either is a logical consequence from the other.

They are not the same: the scientific a.s.sumption is hypothetical, the metaphysical absolute. The former says that things will happen in one way, if certain conditions are fulfilled, in another if they are not; the latter that they absolutely must happen in this way, and not in that; and that it is an illusion to imagine that they can happen _either_ this way _or_ that. Science allows us the alternative; the metaphysical theory declares that the alternative is an impossibility or an illusion. The metaphysical theory may be right, but it is not the same thing as the scientific a.s.sumption. Neither can it be exhibited as a logical presupposition of or consequence from the scientific a.s.sumption. From a hypothetical "if" you cannot logically get an absolute "must." It may be a scientific truth that, if an electric spark is pa.s.sed through two atoms of hydrogen and one of oxygen, a drop of water will be formed. But it does not follow that therefore an electric spark must be pa.s.sed through them.

It is obvious that the difference between science and metaphysics in the matter of necessity is that, whereas science cautiously says, "If certain conditions are fulfilled, certain results will ensue,"

metaphysics boldly says, "The conditions on which the whole future depends are already absolutely fixed." Once more, this metaphysical theory may be true; but, if so, it is not from science that it derives its truth. The transition from the "if" of science to the "must" of metaphysics is illogical, though not unnatural, and is facilitated by a certain amount of obscurity, which can be thrown over it by drawing ill.u.s.trations from the past. Thus, if an event has already taken place, we may infer with certainty from the fact of its occurrence that the conditions necessary to produce it were realised. And as each of those conditions must have had a cause, we can infer again that the conditions requisite to produce them were fulfilled. And so we may travel back _ad infinitum_ along a never-ending chain of cause and effect, always moving from one fixed and necessitated event to another event equally necessitated and fixed. Thus the whole past history of the universe may be exhibited as a necessary sequence of events; and the inference may be drawn, and for the purposes of the theory of metaphysical necessity must be drawn, that because the occurrence of an event proves that the conditions required for its production were realised, therefore they and they alone were bound to be realised. Yet this is simply our old familiar _non sequitur_ thrown into the past tense. It is true that if I walk over a precipice I shall fall, according to the law of gravitation.

But I am not therefore bound to walk over. It is true that the man who fell over the cliff obeyed the law of gravity. But we cannot infer either from the law of gravitation or from the fact of his falling that he was bound to fall. We can infer that the conditions requisite to produce the fall were present, but we cannot infer from the fall that they were bound to be present. It may be quite true that they were bound to be present, but the effect which followed on them cannot be alleged either as the cause or the proof of such necessity. We must look for the reason of the necessity--if there be any necessity in the case--elsewhere. Shall we, then, say that the conditions of the fall were themselves effects of prior causes, without which they would not have happened? That again is true, but the fact that Z would not have happened had not Y preceded, is not in itself any proof that Y was bound to happen. And so we may travel back _ad infinitum_ along the never-ending chain of cause and effect without ever finding ourselves in a position to infer from the law that everything must have a cause, that this cause was bound to operate rather than that. The occurrence of Z is no proof that Y was bound to happen, nor is the fact that Y really happened any proof that its cause X was bound to occur--and so we may work back to the beginning of the alphabet. The fact that B took place shows that A actually occurred, but not that A, rather than A1 or A2, was bound to occur. And if A is the beginning, what was the nature of the necessity (prior to the beginning of things) which determined in favour of A rather than A1 or A2?

We may indeed say, if we like--since no one can prevent us from saying things without proof or probability--that the mere fact that A happened shows that it was bound to happen. But then we might just as well have said it of Z, and saved ourselves the trouble of going through so much alphabet to get so little result. We might just as well say that as the explosion or the accident _did_ happen as a matter of fact, it could not possibly have been prevented: Z was bound to happen under the circ.u.mstances, therefore the circ.u.mstances could not have been altered; only one result was possible under the conditions, therefore no other conditions were possible.

Or--to go back to the beginning of the alphabet once more--we may say with science that we are content with the fact that A did happen, or, since science does not profess to take us back to an absolute beginning (force and matter being eternal and without beginning), let us say we may, like science, be content with the fact that K can be shown to have happened; but whether K, rather than K1 or K2, was bound to occur there is nothing in science to show. If we take up this, the scientific, att.i.tude, two consequences follow. First, there is nothing in science to require or countenance the metaphysical theory of necessity. Next, what is true of K is equally true of L or M or Z. The fact that L or M or Z occurred proves that the conditions did combine in the way necessary to produce L or M or Z, not that they were bound to combine in that way and could not have combined so as to produce L1 or L2, or Z1 or Z2 or Z3.