Integrity without knowledge is weak and useless, and knowledge without integrity is dangerous and dreadful.

The saying balances two virtues often praised in isolation: moral uprightness (integrity) and intellectual competence (knowledge). Johnson’s point is that integrity alone, without the understanding needed to act effectively, can amount to well-meant but ineffectual goodness—“weak and useless.” Conversely, knowledge ungoverned by integrity becomes a tool for manipulation, exploitation, or cruelty—“dangerous and dreadful.” The aphorism thus argues for the inseparability of ethics and intellect in public life and private conduct: ability needs conscience, and conscience needs discernment. It also implies a warning about education divorced from character formation, anticipating later debates about whether learning should cultivate virtue as well as skill.