I have admitted frankly that formal demonstration of our one ultimate obligation is not possible. The final appeal is, and must be, to intuition. The main work of its recommendation consists in the removal of obstacles which obstruct the attainment of that intuition. Trusting that at least something to this end has been achieved by what has been said, I must now invite the reader to give his attention (bearing the foregoing considerations in mind) directly to the crucial experience itself.
Let him imagine himself in a practical situation in which two conflicting ends, x and y, present themselves as rival motives. For convenience, the ends are restricted to two; and, also for convenience, we may choose the simple case of an alternative between doing and forbearing - say indulgence in some drug (x) and abstention from it (y). When he reflects upon these ends (as is natural to a self-conscious being) in relation to the divers goods which he, the common subject of manifold interests, is conscious of wanting, it becomes evident to him at once that to follow x is to bring into hazard much that he holds dear: so much so that, though he 'burns with desire' for it, he cannot regard it as truly representing, in this situation, the good of the self. It is a good, for he is conscious of a desire for it, conscious that it is a satisfaction of his self in one aspect of his being; but it is not the good, for it appears to him as less conducive than y to the satisfaction of the self in its unity or as a whole. y, therefore, presents itself as 'the end of the self-as-such,' as against x, the end of mere desire. In contrast with one another, y is 'self-fulfilling,' and x 'self-destroying.' And what I maintain is that you and I and every other self, when confronted with this plain issue between an end that is self-fulfilling and an end that is self-destroying, do feel, and cannot help feeling, that one 'ought' to resist the latter end and follow the former.
The obligation is just, at bottom, the obligation to respect one's self. It is the obligation to pursue those ends which are truly the ends of the self, in opposition to ends which, while 'desired' by the self, are recognised as not correspondent with the self's fundamental nature, i.e. with its unitary being. Self-consciousness is the awareness on the part of the self of its own unity. The self-conscious self must therefore regard its unitary nature as its 'real' nature, and must regard ends which are not correspondent with that unitary nature (i.e. the ends which are inimical to the good of the self as a whole) as not correspondent with that which is truly its 'self.' The root of morality might thus be said to be the self's obligation to respect, and in respecting to be, its true self. Further than this, in the way of explanation, I do not think it possible to go. If it still be asked why we should be under any obligation to respect what we feel to be our 'real' nature, I think it must be said that there is no answer. We have got down here to a simple bedrock fact of finite rational beings. It is not reasoning now that will help us in assuring ourselves of the obligation's reality, but only actual immersion in the living stream of experience itself. It is at this point that appeal must perforce be made to the reader's own intuition.
Or again, the obligation might be called the obligation to be rational. For this end which we 'ought' to follow is in a special sense the 'end of reason.' It is man's rationality or reflective capacity which forces him to disengage himself from immediate ends and to view them in the light of their contribution to the good of the self as a whole. 'The good of the self as a whole' is thus peculiarly the end sponsored by rational nature. And to describe our obligation in these terms, as 'the obligation to be rational' is to give it what will perhaps be its most generally acceptable formula. The sense of the inherent propriety of 'acting rationally' finds such wide acknowledgment among men that this formula may make appeal to some who are unmoved by the ascription of moral authority to 'self-respect.' But it is only a new formula. We are no nearer than before to an ultimate explanation or justification of the obligation. Immediate experience is, as before, the final court of appeal, the only solvent of ultimate doubts. In the last resort, the proper answer to those who will not acknowledge that there is an obligation to act rationally is just, 'go and see' - or better, 'go and feel'.