The Road to Certainty and Back.

The author relates his intellectual journey from eye-testing clinician to experimental vision scientist. Starting with the quest for underpinning in physics and physiology of vague clinical propositions and of psychology's acceptance of thresholds as "fuzzy-edged," and a long career pursuing a reductionist agenda in empirical vision science, his journey led to the realization that the full understanding of human vision cannot proceed without factoring in an observer's awareness, with its attendant uncertainty and open-endedness. He finds support in the loss of completeness, finality, and certainty revealed in fundamental twentieth-century formulations of mathematics and physics. Just as biology prospered with the introduction of the emergent, nonreductionist concepts of evolution, vision science has to become comfortable accepting data and receiving guidance from human observers' conscious visual experience.