 In later writings, Quine evinces general reservations about the concept of knowledge. One of his favorite objections is that ‘know’ is vague. If knowledge entails certainty, then too little will count as known. Quine infers that we must equate knowledge with firmly held true belief. Asking just how firm that belief must be is akin to asking just how big something has to be to count as being big. There is no answer to the question because ‘big’ lacks the sort of boundary enjoyed by precise words.