Abstract

This paper sets forth a familiar theme, that science essentially consists of two interdependent episodes, one imaginative, the other critical. Hypotheses and other imaginative conjectures are the initial stage of scientific inquiry because they provide the incentive to seek the truth and a clue as to where to find it. But scientific conjectures must be subject to critical examination and empirical testing. There is a dialogue between the two episodes; observations made to test a hypothesis are the inspiration for new conjectures. Inductive generalizations may also inspire hypotheses, but cannot validate them. A hypothesis is empirically tested by ascertaining whether or not predictions about the world of experience deduced from the hypothesis agree with what is actually observed. This has been appropriately considered the 'criterion of demarcation' that distinguishes science from other knowledge. But scientific hypotheses must satisfy other tests as well, e.g., whether they have explanatory value and further understanding. I briefly explore such issues as verifiability and falsifiability, empirical content and truthfulness, contingency and certainty, fact and theory, error and fraud. Science like any human activity is subject to error and to the foibles and other failings of human beings. But severe attempts of empirical falsification and other trials yield knowledge that stands the test of time and provides a foothold for further knowledge. Moreover, scientists have developed social mechanisms, such as peer review and publication, to evaluate their work. Because the research of scientists depends on the validity of previous knowledge, it is of great consequence that they discern valid from invalid knowledge and thus scientists are inclined to transcend ideology, nationality, friendship, monetary interest and other prejudices when the mettle of scientific knowledge is at stake. I use historical examples to illustrate some relevant aspects of scientific practice: its success (Mendel), misrepresentation (Darwin), ideological abuse (Lysenko), arrogant violation of the requirement of testing (Koch), theory replacement (Priestly and Lavoisier, Newton and Einstein), and the indispensability of context (Oswald Avery and Alfred Wegener)