Sympathy, not reason, is the root of moral judgment

Smith argues that before we ever apply an abstract moral rule, we judge others' actions through an instinctive act of imagination: picturing ourselves in their circumstances and noticing whether the resulting feeling in us matches the feeling they display. If someone's grief, anger, or joy seems proportionate to what we imagine we'd feel in their place, we approve of it as fitting; if it seems excessive or absent, we disapprove.

This is a psychological rather than purely logical account of ethics — approval and disapproval are, at root, emotional responses to whether our imagined feelings and another person's actual feelings are in tune with each other. Smith calls this imaginative matching 'sympathy,' using the word more broadly than mere pity to mean any fellow-feeling generated by imagining another's situation.

This grounding in shared feeling, rather than pure logic, is what lets morality function as something social creatures develop together through constant mutual feedback, rather than something derived once by a solitary thinker. We learn right from wrong largely by feeling with others and noticing when our feelings match.