Most of the inventions of men are subject to change. They depend upon humour and caprice. They have a vogue for a time, and then sink into oblivion. It may perhaps be apprehended, that if justice were allowed to be a human invention, it must be placed on the same footing. But the cases are widely different. The interest on which justice is founded is the greatest imaginable, and extends to all times and places. It cannot possibly be served by any other invention. It is obvious, and discovers itself on the very first formation of society. All these causes render the rules of justice steadfast and immutable; at least, as immutable as human nature. And if they were founded on original instincts, could they have any greater stability?
The same system may help us to form a just notion of the happiness, as well as of the dignity of virtue, and may interest every principle of our nature in the embracing and cherishing that noble quality. Who indeed does not feel an accession of alacrity in his pursuits of knowledge and ability of every kind, when he considers, that besides the advantages which immediately result from these acquisitions, they also give him a new lustre in the eyes of mankind, and are universally attended with esteem and approbation? And who can think any advantages of fortune a sufficient compensation for the least breach of the social virtues, when he considers, that not only his character with regard to others, but also his peace and inward satisfaction entirely depend upon his strict observance of them; and that a mind will never be able to bear its own survey, that has been wanting in its parts to mankind and society? But I forbear insisting on this subject. Such reflections require a work apart, very different from the genius of the present. The anatomist ought never to emulate the painter; nor in his accurate dissections and portraitures of the smaller parts of the human body, pretend to give his figures any graceful and engaging attitude or expression. There is even something hideous, or at least minute, in the views of things which he presents; and 'tis necessary the objects should be set more at a distance, and be more covered up from sight, to make them engaging to the eye and imagination. An anatomist, however, is admirably fitted to give advice to a painter; and 'tis even impracticable to excel in the latter art, without the assistance of the former. We must have an exact knowledge of the parts, their situation and connection, before we can design with any elegance or correctness. And thus the most abstract speculations concerning human nature, however cold and unentertaining, become subservient to practical morality; and may render this latter science more correct in its precepts, and more persuasive in its exhortations.
See Appendix at the end of the volume.