Moral Sentiment and Sympathy

The rationalist tradition in ethics — from Plato through Hutcheson's critics to Clarke and Wollaston — holds that moral distinctions are discovered by reason: that right and wrong are objective relations or properties that the intellect can recognise. Hume argues that this cannot be correct, for two reasons. First, reason alone is motivationally inert: it can tell us what is the case but cannot by itself move us to act. Since moral judgments do motivate — the recognition that an action is wrong typically disposes us to avoid it — moral judgment cannot be a purely rational operation. Second, if moral distinctions were purely rational, they would have to be relations of ideas (like mathematics) or matters of fact — and Hume argues that moral rightness and wrongness are neither.

What does ground moral distinctions is the moral sentiments: the specifically moral feelings of approval and disapproval that arise in a calm, impartial observer surveying a character or action. These sentiments are not arbitrary personal reactions but structured responses rooted in human nature — the same across cultures and periods in their basic form, varying only in application. They are grounded primarily in sympathy: the capacity to share in the pleasures and pains of others, to feel their welfare and suffering as if it were our own. Sympathy is not a moral principle but a psychological fact — the natural mechanism by which the happiness of others becomes relevant to our own emotional life.

Since sympathetic responses can be distorted by proximity — we feel more strongly for those close to us — Hume introduces the figure of the impartial spectator: a suitably detached, informed, and calm observer whose approvals and disapprovals represent the objective moral verdict. This figure is not an invention but a correction: we naturally take up this perspective when we want to assess actions fairly. Adam Smith developed this insight into the theory of the impartial spectator that anchors his Theory of Moral Sentiments, and it anticipates the role of the ideal observer in twentieth-century metaethics.

The argument against moral rationalism is most fully developed in Section I and the Appendices of the Enquiry. Hume's most famous formulation of the sentiment-based view — "reason is, and ought only to be the slave of the passions" — appears in the Treatise, Book II, Part III, Section III.