EVERY thought and theory formulated in the past, every phenomenon and phase in the development of the human spirit, can be studied in a double way: either as an incident in the history of ideas, or as an element in the wider history of the human kind. In the former case, the main question to be asked by the historian will concern the content of the thoughts and theories in question, and his prime task will be to comprehend and to evaluate these contents. If he goes beyond them at all, he will either go backwards towards the intellectual antecedents of the ideas he studies, or forward towards their intellectual consequences: but if he has made this particular mode of approach his own he will always remain on the same plane of being, on the intellectual level, the level of ideas. For this reason it has become customary to characterize this method of writing the history of ideas as its treatment ab intra, as its intrinsic study (Innenbetrachtung, as the Germans have it). This must be distinguished from the other approach--the writing of the history of ideas ab extra, its extrinsic study (Aussenbetrachtung). Here it is not so much the content of a thought or theory on which the student concentrates as its relationship to the wider setting within which it has been conceived and born. An idea is not only considered as such, in and for itself, but also as the possible manifestation of wider tendencies, forces or facts, as an expression of realities which lie behind it. In a word, here there is no remaining within the sphere of being called the intellectual life, but a going beyond and beneath and outside it. Hence the name this approach has been given, the label it has received.
'There are two mutually exclusive ways of interpreting ideas,' two well-informed writers have recently explained, 'intrinsically and extrinsically. An intrinsic interpretation is that in which a given product of "mind" is handled as though its significance in form and content lies entirely within itself. Thus, for example, Kant Critique of PracticalReason