Solvency is entirely a matter of temperament and not of income.

The aphorism argues that being financially “solvent” is less determined by how much one earns than by one’s disposition—prudence, restraint, anxiety, optimism, or impulsiveness. Smith compresses a moral-psychological claim into a social observation: two people with the same income can live in radically different financial realities because temperament governs spending, saving, risk-taking, and the ability to delay gratification. The line also gently satirizes the tendency to blame circumstances alone; it implies that character and habit quietly structure economic outcomes. At the same time, its absolutism (“entirely”) is part of the epigram’s bite, provoking readers to test the claim against their own experience.