It is often claimed that science should be "value-free in that ethical, political, and social values have no legitimate role in the justification of scientific theories. Although such values may influence which hypotheses are pursued, or whether some application of scientific theories is desirable, they play no legitimate role in scientific reasoning. ;I argue against the view that all science ought to be value-free. Examining a range of cases from biology, epidemiology, pathology, and atmospheric sciences I show that ethical and (...) political values can operate in cases widely agreed to be "good science." Drawing on recent work by Helen Longino and Phillip Kitcher, I argue that in many research contexts the goals of scientific research cannot be separated from ethical and political interests. As a result, there are at least four ways ethical and political value judgments can play a legitimate role in the justification of scientific theories. First, in certain research contexts, ethical and political values help justify and apply criteria for theory choice . Second, ethical and political aims of inquiry can give scientists reason to adopt conceptual frameworks that contain ethical or political normative content. In these contexts, ethical and political value judgments play a legitimate role as auxiliary hypotheses in generating evidential relations. Third, when scientific research has implications for public policy, scientists must weigh ethical values in determining which risks are "acceptable" in classifying data. Finally, ethical and political considerations can be relevant to evaluating whether an interpretation of data is biased. ;A consequence of my view is that, in some contexts, "value-free" science is not only impossible, but also epistemologically irresponsible. Good science will sometimes require scientists to weigh the ethical and political values at stake in their research. As a result, scientists should be trained to think critically about the ethical and political dimensions of their work. (shrink)