It is generally agreed by historians of modern thought that, at the end of the nineteenth century and the beginning of the twentieth, philosophers in the German-speaking world identified and defined a type or species of knowledge whose peculiar independent status had hitherto been largely overlooked. It was developed, clarified, and, with a sharpened awareness of its unique possibilities, made to work in practice above all by Dilthey, Windelband, Rickert and their numerous followers; and, to a degree, also by Max Weber. The general name by which it was, and is, most often referred to is ‘Verstehen’—understanding. It has to be admitted that it was from the first, and remains to this day, a highly problematic and hotly disputed concept. Positivists, materialists, behaviourists and monists of all kinds—all those whose ideal is a single structure of organized systematic knowledge—have tended to view it with deep suspicion, and even to deny its existence altogether, claiming that it is wholly illusory and doomed to disappear before the inevitable advance of positive scientific method. However that may be, it will not be my purpose in this paper to enter into these difficult controversies. It may indeed be that no watertight definition of it is possible; that its putative boundaries with other forms or types of knowledge are vague and shifting; and even that there is no ultimate discontinuity in principle between it and the knowledge we gain from other spheres of research and investigation.