Even in the case of the intellectual who turns revolutionary, his decision does not arise ex nihilo; it may follow upon a prolonged period of solitude: the intellectual is in search of a doctrine which shall make great demands on him and cure him of his subjectivity; or he may yield to the clear light thrown by a Marxist interpretation of history, in which case he has given knowledge pride of place in his life, and that in itself is understandable only in virtue of his past and his childhood.