T 3.3.1.10

Thus it appears, that sympathy is a very powerful principle in human nature, that it has a great influence on our taste of beauty, and that it produces our sentiment of morals in all |the artificial virtues. From thence we may presume, that it also gives rise to many of the other virtues; and that qualities acquire our approbation, because of their tendency to the good of mankind. This presumption must become a certainty, when we find that most of those qualities, which we naturally approve of, have actually that tendency, and render a man a proper member of society: While the qualities, which we naturally disapprove of, have a contrary tendency, and render any intercourse with the person dangerous or disagreeable. For having found, that such tendencies have force enough to produce the strongest sentiment of morals, we can never reasonably, in these cases, look for any other cause of approbation or blame; it being an inviolable maxim in philosophy, that where any particular cause is sufficient for an effect, we ought to rest satisfied with it, and ought not to multiply causes without necessity. We have happily attain'd experiments in the artificial virtues, where the tendency of qualities to the good of society, is the sole cause of our approbation, without any suspicion of the concurrence of another principle. From thence we learn the force of that principle. And where that principle may take place, and the quality approv'd of is really beneficial to society, a true philosopher will never require any other principle to account for the strongest approbation and esteem.