In her first book, "Science as Social Knowledge" (1990), Longino argued for the relevance of social values, or values which are part of the human context of science, to the justification of scientific knowledge as objective. In her contextual empiricism, she argues that observations and data of the sort taken by scientists are not by themselves evidence for or against any particular hypotheses. Rather, the relevance of any particular data for any given hypothesis is decided by human beliefs and assumptions about what kinds of data can support what kinds of hypotheses. Moreover, even when the relevance of evidence is decided, there remains a logical gap between evidence and full justification of interesting scientific theories (the traditional philosophical problem of underdetermination of theories). This gap, too, must be bridged by beliefs and assumptions about legitimate reasoning in order for evidence to help us decide which hypotheses to accept as true.