How wonderful that we have met with a paradox. Now we have some hope of making progress.

Bohr’s remark captures a characteristic attitude in early quantum theory: apparent contradictions are not merely obstacles but signals that existing concepts are inadequate. In domains like atomic structure and wave–particle duality, classical intuitions produced paradoxes that forced physicists to revise foundational assumptions and develop new formalisms. The quote suggests that genuine progress often begins when a problem resists tidy resolution—when a paradox exposes hidden premises and opens a path to deeper, more comprehensive understanding. It also reflects Bohr’s broader philosophical stance (often associated with complementarity): mutually exclusive descriptions may both be necessary to account for phenomena at the limits of human concepts.