The supreme rule is the authority over all the faculties and impulses; and is made up of the partial rules according to the separate faculties, powers, and impulses.  We are to look, in the first instance, to the several faculties or departments of the mind; for, in connexion with each of these, we shall find an irresistible propriety inherent in the very nature of the faculty.

For example, man lives in the society of fellow-men; his actions derive their meaning from this position.  He has the faculty of Speech, whereby his actions are connected with other men.  Now, as man is under a supreme moral rule, [this the author appears to assume in the very act of proving it], there must be a rule of right as regards the use of Speech; which rule can be no other than truth and falsehood.  In other words, veracity is a virtue.

Again, man, as a social being, has to divide with others the possession of the world, in other words, to possess Property; whence there must be a rule of Property, that is, each man is to have his own.  Whence Justice is seen to be a virtue.

The author thinks himself at one with the common notions of mankind in pronouncing that the Faculty of Speech, the Desire of Possessions, and the Affections, are properly regulated, not by any extraneous purposes or ends to be served by them, but by Veracity, Justice, and Humanity, respectively.

He explains his position farther, by professing to follow Butler in the doctrine that, through the mere contemplation of our human faculties and springs of action, we can discern certain relations which must exist among them by the necessity of man’s moral being.  Butler maintains that, by merely comparing appetite with conscience as springs of action, we see conscience is superior and ought to rule; and Whewell conceives this to be self-evident, and expresses it by stating that the Lower parts of our nature are to be governed by the Higher.  Men being considered as social beings, capable of mutual understanding through speech, it is self-evident that their rule must include veracity.  In like manner, it is self-evident from the same consideration of social relationship, that each man should abstain from violence and anger towards others, that is, love his fellow men.

Remarking on the plea of the utilitarian, that truth may be justified by the intolerable consequences of its habitual violation, he urges that this is no reason against its being intuitively perceived; just as the axioms of geometry, although intuitively felt, are confirmed by showing the incongruities following on their denial.  He repeats the common allegation in favour of a priori principles generally, that no consideration of evil consequences would give the sense of universality of obligation attaching to the fundamental moral maxims; and endeavours to show that his favourite antithesis of Idea and Fact conciliates the internal essence and the external conditions of morality.  The Idea is invariable and universal; the Fact, or outward circumstances, may vary historically and geographically.  Morality must in some measure be dependent on Law, but yet there is an Idea of Justice above law.