That is what learning is. You suddenly understand something you've understood all your life, but in a new way.

Lessing defines learning not as the accumulation of new facts but as a shift in perception: an old, half-known truth becomes fully intelligible when seen from a fresh angle. The paradox—"you suddenly understand something you've understood all your life"—captures how experience, maturity, or changed circumstances can reconfigure meaning. What once felt like vague familiarity becomes articulated insight. The line also implies that education is iterative and reflective: understanding deepens through re-seeing rather than merely receiving. In Lessing’s broader concerns as a writer—psychological development, social conditioning, and the limits of conventional wisdom—the quote suggests that genuine learning is transformative, altering the learner’s relationship to what they thought they already knew.