Nearly all philosophers have dealt with the outcomes of scientific research, and have overlooked its philosophical presuppositions, such as those of rationality and realism. Although these presuppositions are mostly tacit and thus easily overlooked, actually they are supremely important, since some of them favor research whereas others hamper it. For instance, whereas subjectivism leads to navel gazing and uncontrolled fantasy, realism encourages us to explore the world and check our conjectures.This book examines science in the making, a process it illustrates with many examples from the natural, social, and biosocial sciences. Therefore it centers on the research process and its philosophical presuppositions. It claims that the latter constitutes a sort of matrix for conceiving and nurturing scientific projects.