Essays in Experimental Logic — John Dewey

But since one does not think about knowledge except when he is thinking, except, that is, when the intellectual or cognitional interest is dominant, the professional philosopher is only too prone to think of all experiences as if they were of the type he is specially engaged in, and hence unconsciously or intentionally to project its traits into experiences to which they are alien. Unless he takes the simple precaution of holding before his mind contrasting experiences like those just mentioned, he generally forms a habit of supposing that no qualities or things at all are present in experience except as objects of some kind of apprehension or awareness.