What did Husserl mean by knowledge of essences?

In the context of phenomenology, Edmund Husserl’s "knowledge of essences" refers to the grasp of the eidos—the invariable, necessary structure of a thing, distinct from its contingent or accidental features. This knowledge is not achieved through empirical generalization or abstract induction, but through a methodological process known as eidetic reduction.12

To attain this insight, Husserl employed a technique called free variation. Starting with a concrete object, the philosopher imaginatively varies its different aspects; the essence is the "invariant"—the identical structure that remains unchanged throughout this process of variation. This act of grasping essences, or Wesensschau, relies on intuition to perceive these structures immediately in their presence.12

By focusing on these universal structures rather than factual, accidental occurrences, phenomenology aims to function as a "rigorous science" that explores the foundations of meaning within consciousness. This approach allows for the discovery of synthetic a priori truths, which are independent of experience yet grounded in the essential relationships observed within the phenomena.234