The metaphysical department of the Treatise is a system with a great leading principle throughout, of which its author intended that all the details should be but the individual applications. If his reasoning in that department of his work be accurate, he sweeps away all other systems of the foundation of knowledge, and substitutes another in their stead. But the third book, "on Morals," like the second, on "the Passions," has no such pretension. The leading principles of the metaphysical department are certainly kept in view, but the details are not necessarily parts of it. They have a separate existence of their own: they are an analysis of phenomena which we witness in our daily life; and the reader assents or dissents as the several opinions expressed correspond with or diverge from his own observation of what he sees passing in the world around him, without, in that mental operation, either receiving or rejecting any general theory. In short, it is to a considerable extent a series of observations of human conduct and character; and as such they are admitted or denied, are sympathized with or contemned, according to the previous feelings and opinions of the reader. Among the prominent features of the theoretical part of this book, is the admission of a moral sense,[121:1] but the negation of an abstract code of morality, separately existing, and independent of the position of the persons who are applying this sense. The work in some measure foreshadows the systems which have been respectively called the utilitarian and the selfish; the former applying as the scale of moral excellence the extent to which an action is beneficial or hurtful to the human race; the latter referring the actions of mankind, whether good or bad, interested or disinterested, to self, and to impulses which are always connected with the individual in whom they act, and his passions or desires.