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.

He sums up the chapter thus:—­’That, by an original power of the mind, which we call conscience, or the moral faculty, we have the conceptions of right and wrong in human conduct, of merit and demerit, of duty and moral obligation, and our other moral conceptions; and that, by the same faculty, we perceive some things in human conduct to be right, and others to be wrong; that the first principles of morals are the dictates of this faculty; and that we have the same reason to rely upon those dictates, as upon the determinations of our senses, or of our other natural faculties.’  Hamilton remarks that this theory virtually founds morality on intelligence.

Moral Approbation is the affection and esteem accompanying our judgment of a right moral act.  This is in all cases pleasurable, but most so, when the act is our own.  So, obversely, for Moral Disapprobation.

Regarding Conscience, Reid remarks, first, that like all other powers it comes to maturity by insensible degrees, and may be a subject of culture or education.  He takes no note of the difficulty of determining what is primitive and what is acquired.  Secondly, Conscience is peculiar to man; it is wanting in the brutes.  Thirdly, it is evidently intended to be the director of our conduct; and fourthly, it is an Active power and an Intellectual power combined.

ESSAY IV. is OF THE LIBERTY OF MORAL AGENTS, which we pass by, having noticed it elsewhere.  ESSAY V. is OF MORALS.

Chapter I. professes to enumerate the axiomatic first principles of Morals.  Some of these relate (A) to virtue in general:  as (1) There are actions deserving of praise, and others deserving blame; (2) the involuntary is not an object of praise or blame; (3) the unavoidable is not an object of praise or blame; (4) omission may be culpable; (5) we ought to inform ourselves as to duty; (6) we should fortify ourselves against temptation.  Other principles relate (B) to particular virtues:  (1) We should prefer a greater good to a less; (2) we should comply with the intention of nature, apparent in our constitution; (3) no man is born for himself alone; (4) we should judge according to the rule, ‘Do to others,’ &c.; (5) if we believe in God, we should venerate and submit to him.  A third class of principles (C) settle the preference among opposing virtues.  Thus, unmerited generosity should yield to gratitude, and both to justice.