IV. Thought as the Instrument of Knowledge

Whatever principle we choose to lay down, we must prove that somewhere we have observed it, or we must enunciate it in the form of a clear concept which can be rethought by any other thinker. Every philosopher who sets out to discuss his fundamental principles, must express them in conceptual form and thus use thought. He therefore indirectly admits that his activity presupposes thought. We leave open here the question whether thought or something else is the chief factor in the development of the world. But it is at any rate clear that the philosopher can gain no knowledge of this development without thought. In the occurrence of phenomena thought may play a secondary part, but it is quite certain that it plays a chief part in the construction of a theory about them.