If one is willing to speak about mathematical proof in Wittgenstein, one must take into account that for him, in philosophy, "... we are not laying foundations, but tidying up a room, in the process of which we have to touch everything a dozen times. The only way to do philosophy is to do everything twice".¹ Thus, it does not come as a surprise that several times he goes over the same subject, and that it is practically impossible to obtain, by this token, a unique solution, a definite idea, a great global vision of the questions he poses.