Compassion of tenderness or friendship; and envy is naturally accompanied with anger or ill-will. To desire the happiness of another, from whatever motive, is a good preparative to affection: And to delight in another’s misery almost unavoidably begets aversion towards him.
… A partner is a natural object of friendship; a rival of enmity.
Hume notes “natural laws” of human begins. He often states the obvious, sometimes nearing tautologies: we give affection to the people we like and we push away the people we dislike.
As hatred produces a desire of the misery, and an aversion to the happiness of the person hated. These opposite desires seem to be originally and primarily conjoined with the passions of love and hatred. It is a constitution of nature, of which we can give no farther explication.
These observations are important for the sequel of the study on feelings: humans naturally behave this way, in a more or less inexplicable and irrational fashion; they do not decide what pleases them, they directly feel the effects of beauty (and deformity).
The takeaway for the upcoming of the series is that we naturally demonstrate compassion towards our partners (people we surround ourselves of because we find them desirable, pleasant); inversely, we demonstrate aversion towards our rivals (people who covet the same things as us and who are too close to our liking, which causes an unpleasant feeling).