In order to explain the causes of these passions, we must reflect on certain properties, which, tho’ they have a mighty influence on every operation, both of the understanding and passions, are not commonly much insisted on by philosophers.
In his preliminary interrogations on the passions, Hume tries to determine their causes, and more specifically the root principles of these causes. His method, as a reminder, is that of empiricism, driven from experience, simple observation.
He notes three principles describing the workings of the passions:
- association of ideas (it is natural to jump from one idea to another, given there is something linking the two);
- association of resembling emotions (grief and disappointment are often followed by anger and envy, and even malice, then grief again);
- the association between two emotions is even greater when both concur in the same thing (an angry person will find even more pretexts to justify their irritation before other people).
Thus, a man, who, by any injury from another, is very much discomposed and ruffled in his temper, is apt to find a hundred subjects of hatred, discontent, impatience, fear, and other uneasy passions; especially, if he can discover these subjects in or near the person, who was the object of his first emotion. Those principles, which forward the transition of ideas, here concur with those, which operate on the passions; and both, uniting in one action, bestow on the mind a double impulse.
These chaining effects noted by Hume are simply allowed by transitivity: an unpleasant impression carries another similar one, equally unpleasant, as it occurs while passing from cry to anger, hatred, resentment. This also holds for pleasant emotions: we are more generous when we are already in a good mood, when seeing a person which appears to us as pretty or elegant, and our own good will provides us with even more well-being.
According to Hume, such relations, pleasant or unpleasant, are tightly linked to equally opposite feelings—pride and humility—which are fundamental to understand the workings of love.