Hartley's analysis of the moral sense is a great advance upon Hobbes and Mandeville, who make self-love the immediate constituent, instead of a remote cause, of conscience. Our moral consciousness may thus be treated as peculiar and distinguishable from other mental states, while at the same time it is denied to be unique and irresolvable. THOMAS REID.[24] [1710-96.] Reid's Ethical views are given in his Essays on the Active Powers of the Mind. ESSAY III., entitled THE PRINCIPLES OF ACTION, contains (Part III.) a disquisition on the _Rational Principles of Action_ as opposed to what Reid calls respectively _Mechanical_ Principles (Instinct, Habit), and _Animal_ Principles (Appetites, Desires, Affections). The Rational Principles of Action are Prudence, or regard to our own good on the whole, and Duty, which, however, he does not define by the antithetical circumstance--the 'good of others.' The notion of Duty, he says, is too simple for logical definition, and can only be explained by synonymes--_what we ought_ to do; what is fair and honest; what is approvable; the professed rule of men's conduct; what all men praise; the laudable in itself, though no man praise it. Duty, he says, cannot be resolved into Interest. The language of mankind makes the two distinct. Disregard of our interest is folly; of honour, baseness. Honour is more than mere reputation, for it keeps us right when we are not seen. This principle of Honour (so-called by men of rank) is, in vulgar phrase, honesty, probity, virtue, conscience; in philosophical language, the moral sense, the moral faculty, rectitude. The principle is universal in men grown up to years of understanding. Such a testimony as Hume's may be held decisive on the reality of moral distinctions. The ancient world recognized it in the leading terms, _honestum_ and _utile_, &c. The abstract notion of Duty is a relation between the action and the agent. It must be voluntary, and within the power of the agent. The opinion (or intention) of the agent gives the act its moral quality. As to the Sense of Duty, Reid pronounces at once, without hesitation, and with very little examination, in favour of an original power or faculty, in other words, a Moral Sense. Intellectual judgments are judgments of the external senses; moral judgments result from an internal moral sense. The external senses give us our intellectual first principles; the moral sense our moral first principles. He is at pains to exemplify the deductive process in morals. It is a question of moral reasoning, Ought a man to have only one wife? The reasons are, the greater good of the family, and of society in general; but no reason can be given why we should prefer greater good; it is an intuition of the moral sense.