This is an original book on the philosophy of medicine. It considers philosophy of medicine as a subdiscipline of philosophy of science. This volume is grounded on an epistemological bottom-up account that arises from the clinical situation, the epidemiologic, and the resulting public health account. It is not a review of the literature, and it is not intended to frame the debates, or to analyze and compare the various number of viewpoints. Medicine is the human activity, which begins by a linguistic act that identifies the negative norms of health: it begins with a first distinction that splits biological processes into three conventional parts, normal, abnormal and pathologic. Neither of them is a natural kind. Being abnormal is intrinsically bad and admits of degrees, while being pathologic is dichotomous. Being normal is factitious and counterfactual much the same as frictionless planes in physics. Leaving apart the ethical aspects, this book endeavors to uncover the implicit conceptual network, the chief junctures of medicine, should they be found, and their articulations with clinical and community medicine. It results that medicine is pervaded with dichotomous concepts such as scientific vs pragmatic discourse, function and malfunction, abnormal and pathologic, needs and wants, causation and explanation, clinical vs community-oriented care, physical vs psychiatric diseases, mental illness vs deviancy, and so on. Medical thinking has two dimensions intrinsically interweaved, namely a constant amalgam and admixture of biological and normative aspects, so that this essential hybrid nature of the grammar of medicine endorses opposite approaches, naturalistic or normativist, biological or value-laden, realist or instrumental, reductionist or holistic, phenomenological or analytic.