Every great advance in science has issued from a new audacity of imagination.

The line links scientific progress to a creative leap: major breakthroughs do not arise from cautious accumulation alone, but from imaginative risk-taking that proposes new possibilities before they can be fully justified. “Audacity” suggests a willingness to challenge reigning assumptions, to entertain hypotheses that initially look speculative, and to reframe problems in novel ways. Read in a pragmatist key often associated with Dewey, the quote underscores that inquiry is an active, inventive practice: imagination helps generate the questions, models, and conceptual tools that experiments later test and refine. The significance is a corrective to portrayals of science as purely mechanical or rule-bound, emphasizing its inventive, human dimension.