What we ordinarily say, we say unclearly. We speak unclearly because we think unclearly. It is the task of philosophy to render our thoughts clear. … We cannot clarify our thoughts by thinking about thinking, nor by thinking about logic. We have to think about what we were thinking about. The philosopher considers a given expression, and analyses it in order to find another expression which says more clearly what the original expression said less clearly. This investigation is not linguistic. We