Abstract
This is the sixth volume of the Opus series on the history of western philosophy. It is not intended for the novice but for readers who already have at least some familiarity with philosophical issues. Of necessity, some philosophers who did not write in English are covered; Frege of course is discussed and, more briefly, some of the late nineteenth-century scientist-philosophers like Mach and Poincaré. Because of the pervasive influence of Kant, brief and rather sketchy accounts of the "critical philosophy" are found also, but readers who hope to profit from Skorupski's discussion had best have a prior acquaintance with Kant's work.