Whether the conditions combine so as to produce A, or so as to produce B, the uniformity of nature is equally obeyed in either case, the law that a cause must produce its effect is equally fulfilled, and either sequence is as amenable to scientific explanation as the other. But though science and the uniformity of nature both require us to believe that when the conditions are combined the result will follow, neither requires us to assume that the combination is fixed before it is effected. And this is true equally of purely physical events and of human actions. This truth, in the case of the latter class of actions, is expressed by the statement that alternative courses of action are open to the agent, and that they are real alternatives, alternatives such that any one of them may in this particular instance be followed. From the point of view of science and of the uniformity of nature, we do not conceive that there is any difference in this respect between human actions and physical events: if science is to include both kinds of sequence and to render a rational account of them, we must assume that the principles on which conditions combine or fail to combine are the same in both cases. If physical events and human actions are both constituents in the process of evolution, there must be a continuity between them. It follows, therefore, that, in the case of physical events as well as of human actions, until the conditions are combined in such a way as to involve one determinate result to the exclusion of all others, they might combine in other ways with other results—in fine, that before the combination is effected there are always other alternatives.
At this point it becomes necessary to take into account the diversity as well as the uniformity of nature—in this case a diversity which will lead us to a higher uniformity. To the human agent alternative courses of action are open in the sense that he is conscious of their possibility and that after deliberation he adopts one or other of them. With purely physical phenomena and material things the case is different: they may be combined in this way or in that; the alternative is indeed open, so long as the combination is not effected, but it is not open to them nor is it adopted, when adopted, by them. It is adopted for them. In some cases by man. In all cases by that by which alone alternative courses of action can be contemplated and adopted—a conscious will. The course and form which man imparts to material things—to his implements or his works of art—make them so far the expression of his will; for the rest they are equally an expression of will, though of a will not his.
For those at the present day who unfeignedly accept the general principles of evolution and philosophise from them, a dualistic philosophy is impossible. They cannot hold that matter is subject to evolution and that mind is not; and the continuity of the process of evolution forbids us to suppose that there is any real discontinuity between that which appears at one stage as matter and at another as mind. There is no discontinuity if material things (i.e. the things of which we have sense-perception, but which differ from our sensations in being permanent) are on the one side the permanent expressions of Will and on the other are the transient impressions made on us in the shape of sense-phenomena.
What is true thus of the content of evolution, of that which is in process of evolution, is true also of the law of the process. We cannot suppose that it extends only to matter—that the behaviour of matter is susceptible of a rational explanation and the behaviour of mind is not. The continuity of the process excludes the possibility of a dual control: either the power which manifests itself in all things is intelligent throughout or it is not. If there is no reason in the behaviour of things, but only necessity, then those human actions and conceptions which man considers to be the result of his reason are really the result of unintelligent necessity.
It is the latter hypothesis which is expressed by the necessitarian theory. The ordinary belief of mankind—a belief which it is impossible to resist at the moment when you are making up your mind whether you will do this or not—is that you can do the thing or not, that the alternatives are real and the motives such that either of them may be acted on. The necessitarian hypothesis is that the alternatives are not real, that even before you have made up your mind there is only one alternative which you can follow—the other courses are only apparent alternatives, because you cannot choose or act on any of them; the other motives are not real motives, because by a necessity dating from the beginning of things they cannot possibly influence you on this occasion. Your action is as automatic as that of a piano which responds to the touch. The difference is that you think about the stimulus received and the piano does not. Consequently the piano makes no mistakes; you make two. You think of various possible consequences of the stimulus—which are all impossible—and you imagine that the one which you choose is the consequence of your intelligent choice, whereas it is the automatic outcome of that iron law of necessity which binds together the whole process of evolution.
It will be readily understood that a hypothesis of this kind, which is apparently in violent conflict with the plainest facts of our daily personal experience, and gives the lie to that consciousness of freedom which we all possess, would not be held in theory—it cannot be acted on in practice—unless it appeared to be the consequence of some well-established facts. It is, of course, held by its supporters to be a logical consequence from the uniformity of nature and the law of universal causation, and to be a necessary pre-supposition if we are to give any scientific account of human nature and its evolution. If, as we have argued at length in this chapter, that is not the case, if the law of universal causation only requires that a thing cannot take place unless the requisite conditions combine—and not that conditions, which did or may combine, were or are bound to combine—the question still remains, what if any value the hypothesis has on its own intrinsic merits.
In the first place it is a hypothesis which can never either be proved or disproved. The hypothesis is that our supposed consciousness of freedom is an illusion, that if we imagine we are free to choose what we will do, or that we could in the past have chosen otherwise than we did, we are deceived. The hypothesis is not based on any facts of consciousness: it is a suggestion that consciousness may be deceptive. It may: there is no means of proving or disproving the suggestion, for any reply must proceed from one consciousness to another, both of which are suspected by the maker of the suggestion to be not wholly trustworthy. We cannot ask him to concede to us, in order that we may convince him by argument, the very point which is in dispute.
In the next place, the hypothesis of necessity does formally account for all the facts which it is designed to explain: it accounts for the whole process of evolution. If everything that happens does so because it must, then the mere occurrence of any step in the process carries its own explanation with it: the mere fact that it occurred shows that it was bound to occur. If we ask, "Why was it bound to occur?" the answer is, "Because it was." Various intermediate reasons may be interpolated—because everything must have a cause, and every cause must have its effect—but if we ask, "Why must everything have a cause? why must every cause produce its effect?" the ultimate answer is always, "It must because it must." If we ask, "What proof is there that it must?" there is none. As we have already said, the hypothesis is one which does not admit either of proof or disproof.
The case is much the same with the opposite theory of freedom. Formally, the hypothesis that the whole process of evolution is throughout the expression of self-determining will is adequate to account for all the facts. But it is a hypothesis which can be neither proved nor disproved if the testimony of consciousness to our freedom may not be accepted. We cannot prove that the testimony of consciousness is true or to be trusted in this or any other matter. We take it on faith. The questions arise, therefore, Is it reasonable to take anything on faith? and if so, what? and why?