THIS remark is often repeated in textbooks and manuals on modem physics. It is singled out here for several reasons: (i) Its innocent, matter-of-fact tone conceals one of the most intricate and interesting chapters in the history of scientific discovery; (2) it encourages an analogy between discoveries within microphysics, and quite noncomparable discoveries within, e.g., natural history; and (3) the actual discovery of the positron, in all its dimensions, constitutes an instructive example of the interplay of theory and experiment within physical science, one of the best a historian, or logician, of science could ever hope for. The positron packet can be dipped into in three different ways. The physicist reaches into this complex of concepts to facilitate his thinking within e.g. quantum field theory, or the experimental study of cosmic rays. The historian of physics attends to the exciting interplay of ideas within the microphysics of the 1920s--the better to perceive the initial resistance to the positron-idea, as well as to trace the theoretical evolution which resulted in the claim that positive electrons exist. The logician will focus upon the internal structure of the arguments and concepts actually employed, and still being employed, by those physicists who have played major roles in this story. In the history of science the positron discovery constitutes at once one of the richest, and yet one of the most neglected, areas of inquiry. The discovery of the positive electron was a discovery of three different particles. I choose to put the matter this way, rather than to