Traditionally, studies in the philosophy of biology have been strongly centered on evolutionary biology and systematics. To be sure, during the last four decades the field of molecular biology has been subject to substantial philosophical discussion as well. Still, discussions of molecular biology have focused on questions peculiar to this field (such as the relation between classical and molecular genetics). The first exception to this rule was Ken Schaffner’s Discovery and Explanation in Biology and Medicine (1993), a monograph which addressed general philosophy of science questions from the point of view of molecular and experimental biology. A decade has passed since Schaffner’s seminal account of discovery and theorizing in molecular biology, but recently another book on this topic has appeared: Marcel Weber’s Philosophy of Experimental Biology (2004). I feel that Weber’s treatment will move the philosophical discussion well beyond Schaffner’s original study. Like Schaffner before him, the particular strength of Weber lies in combining two ideals. First, his philosophical discussion is based on detailed case studies from biochemistry, molecular biology, cellular biology, developmental genetics, and neurophysiology. Second, despite closeattention to actual science, Weber always keeps questions from the general philosophy of science clearly in view.