A Treatise of Human Nature by David Hume — Read

Thus in whatever light we consider this subject, we may still observe, that die causes of pride and humility correspond exactly to our hypothesis, and that nothing can excite either of these passions, unless it be both related to ourselves, and produces a pleasure or pain independent of the passion. We have not only proved, that a tendency to produce pleasure or pain is common to all the causes of pride or humility, but also that it is the only thing, which is common; and consequently is the quality, by which they operate. We have farther proved, that the most considerable causes of these passions are really nothing but the power of producing either agreeable or uneasy sensations; and therefore that all their effects, and amongst the rest, pride and humility, are derived solely from that origin. Such simple and natural principles, founded on such solid proofs, cannot fail to be received by philosophers, unless opposed by some objections, that have escaped me.

It is usual with anatomists to join their observations and experiments on human bodies to those on beasts, and from the agreement of these experiments to derive an additional argument for any particular hypothesis. It is indeed certain, that where the structure of parts in brutes is the same as in men, and the operation of these parts also the same, the causes of that operation cannot be different, and that whatever we discover to be true of the one species, may be concluded without hesitation to be certain of the other. Thus though the mixture of humours and the composition of minute parts may justly be presumed so be somewhat different in men from what it is in mere animals; and therefore any experiment we make upon the one concerning the effects of medicines will not always apply to the other; yet as the structure of the veins and muscles, the fabric and situation of the heart, of the lungs, the stomach, the liver and other parts, are the same or nearly the same in all animals, the very same hypothesis, which in one species explains muscular motion, the progress of the chyle, the circulation of the blood, must be applicable to every one; and according as it agrees or disagrees with the experiments we may make in any species of creatures, we may draw a proof of its truth or falshood on the whole.