Until fairly recently a common way of doing history of science was to pick up an important strand of contemporary scientific thought and to trace its origin back to the philosophical tangle of the scientific revolution. This approach conveniently by-passed the breakdowns of once useful and pervasive theories, and neglected the long intellectual journeys along devious routes. History of science read like a success story; the pioneers who failed were neither dismissed nor excused; they were simply ignored. The historian knew (...) what he was hunting for and he was careful to limit his search to areas where his quarry was sure to be found. This method, which has been dubbed the precursor-view, stands in contrast—albeit, not in opposition—to the contextual method, which aims at a better understanding of the actual thought-processes of the early scientists. On this second view, history of science must not only account for present theories in the light of past developments, it must also assess old theories in terms of the scientist's conceptual framework, and judge them against the background of the world picture of his age. This may lead the historian down the blind alleys of the past, chasing spurious attempts at explaining the nature of physical reality, but it can clear the ground for a less anachronistic interpretation of the emergence of modern science and the actual process of discovery. History of science acts as a winnowing fork, but we cannot suppose that the discoverer himself always separated the wheat from the chaff, and we must be ever wary of equating the dream with the task. (shrink)