How much pain they have cost us, the evils which have never happened.

Jefferson’s line laments the self-inflicted suffering produced by anxiety and anticipation. The “evils which have never happened” are imagined catastrophes—political, personal, or moral—that occupy the mind as if they were real, exacting an emotional toll despite never materializing. The aphorism aligns with a long classical and Enlightenment tradition (often associated with Stoic moral psychology) that distinguishes between actual misfortune and the mind’s projections. Its significance lies in its practical ethical counsel: to govern one’s fears, resist speculative dread, and measure distress by realities rather than possibilities. In Jefferson’s political world, it also resonates as a warning against panic-driven judgments and policies.