For popular use this definition is amply sufficient, but it still falls short of the complete accuracy required for the purposes of the philosopher. Political Economy does not treat of the production and distribution of wealth in all states of mankind, but only in what is termed the social state; nor so far as they depend upon the laws of human nature, but only so far as they depend upon a certain portion of those laws. This, at least, is the view which must be taken of Political Economy, if we mean it to find any place in an encyclopedical division of the field of science. On any other view, it either is not science at all, or it is several sciences. This will appear clearly, if, on the one hand, we take a general survey of the moral sciences, with a view to assign the exact place of Political Economy among them; while, on the other, we consider attentively the nature of the methods or processes by which the truths which are the object of those sciences are arrived at. Man, who, considered as a being having a moral or mental nature, is the subject-matter of all the moral sciences, may, with reference to that part of his nature, form the subject of philosophical inquiry under several distinct hypotheses. We may inquire what belongs to man considered individually, and as if no human being existed besides himself; we may next consider him as coming into contact with other individuals; and finally, as living in a state of _society_, that is, forming part of a body or aggregation of human beings, systematically co-operating for common purposes. Of this last state, political government, or subjection to a common superior, is an ordinary ingredient, but forms no necessary part of the conception, and, with respect to our present purpose, needs not be further adverted to. Those laws or properties of human nature which appertain to man as a mere individual, and do not presuppose, as a necessary condition, the existence of other individuals (except, perhaps, as mere instruments or means), form a part of the subject of pure mental philosophy. They comprise all the laws of the mere intellect, and those of the purely self-regarding desires. Those laws of human nature which relate to the feelings called forth in a human being by other individual human or intelligent beings, as such; namely, the _affections_, the _conscience_, or feeling of duty, and the love of _approbation_; and to the conduct of man, so far as it depends upon, or has relation to, these parts of his nature--form the subject of another portion of pure mental philosophy, namely, that portion of it on which _morals_, or _ethics_, are founded. For morality itself is not a science, but an art; not truths, but rules. The truths on which the rules are founded are drawn (as is the case in all arts) from a variety of sciences; but the principal of them, and those which are most nearly peculiar to this particular art, belong to a branch of the science of mind.