The present Essay has to inquire into the way in which we may determine what the end of human conduct is,--into the basis of ethics, therefore. But I do not propose to offer an exhaustive investigation of all the theories which have been or may be started in solution of the problem. On the contrary, I will begin by excluding from the inquiry all theories which seek the basis of ethics in something outside the constitution of man as a feeling and reasoning agent:[11] not because I contend that all such theories are _primâ facie_ unreasonable, but because it is at any rate the more obvious course to seek to determine the function of an organism by studying its inner constitution, than by having regard to something which is external to it, and does not act upon and modify it as a necessary part of its environment. It is only when this method has been tried and has failed that we should seek outside us for some guide as to the part we ought to play in the universe. For this reason I shall not take into consideration the views of the basis of ethics which find it in positive law either divine or human, except in so far as they are shown to follow from the nature of man. It is not necessary for me to deny that the source of all moral obligation may be the will of God, or the commands of the sovereign, or the opinion of society, and that the highest moral ideal may be obedience to such a rule. But theories of this kind make ethics merely an application of positive theology, or of legislation, or of social sentiment, and seem only to have an appropriate place when we have failed to find an independent basis for action. The question which remains to be put may be expressed in these terms: Can we find in human nature (taken either alone or in connection with its environment) any indications of the end of human conduct, or, in other words, of the principle on which human beings "ought" to act? and if so, in what direction do these indications point, and what is their significance? The answer to this question will thus necessarily depend on the view we take of the constitution of man and his relation to his environment. And I purpose to bring this discussion within the necessary limits by considering the ethical consequences of one only of the two views into which philosophical opinion is divided. [Sidenote: and here to ethics of Naturalism,] [Sidenote: as distinguished from Rational ethics.] [Sidenote: Naturalism either individualistic] [Sidenote: or historical.]