It is to be observed, however, that precisely similar arguments might be urged against our affirmation of purpose, design, will, as the spring of the actions of other human beings.[3] For let us consider why it is that, mind being assumed as the basis of our own individual consciousness, we go on to attribute minds of like character to other men. We see that the external behaviour of other men is similar to our own, and that the most reasonable way of accounting for such behaviour is to suppose that they have minds like ourselves, that they are possessed of an active and spontaneously energising faculty, which is the seat of their personality. But it is instructive to observe that neither on Kantian principles nor on any other can we _demonstrate_ this; to cross the chasm which separates one man’s personality from another’s requires a venture of faith just as emphatically as any theological formula. I can by no means _prove_ to the determinant Judgement that the complex of sensations which I constantly experience, and which I call the Prime Minister, is anything more than a well-ordered machine. It is improbable that this is the case--highly improbable; but the falsity of such an hypothesis cannot be proved in the same way that we would prove the falsity of the assertion that two and two make five. But then though the hypothesis cannot be thus ruled out of court by demonstration of its absurdity, it is not the simplest hypothesis, nor is it that one which best accounts for the facts. The assumption, on the other hand, that the men whom I meet every day have minds like my own, perfectly accounts for all the facts, and is a very simple assumption. It merely extends by induction the sphere of a force which I already know to exist. Or in other words, crude materialism not giving me an intelligent account of my own individual consciousness, I recognise mind, νοῦς, as a _vera causa_, as something which really does produce effects in the field of experience, and which therefore I may legitimately put forward as the cause of those actions of other men which externally so much resemble my own. But, as has been said before, this argument, though entirely convincing to any sane person, is not demonstrative; in Kantian language and on Kantian principles the reasoning here used would seem to be valid only for the reflective and not for the determinant Judgement. If the principle of design or conscious adaptation of means to ends be not a constitutive principle of experience, but only a regulative principle introduced to account for the facts, what right have we to put it forward dogmatically as affording an explanation of the actions of other human beings?