L. Wittgenstein. University Of Chicago Press, Chicago, (Oktober 1989)characterizes mathematical propositions: - Do not have a temporal sense (pp. 34). - Are rules of expression. "the connection between a mathematical proposition and its application is roughly that between a rule of expression and the expression itself in use" (pp. 47). A rule of expression defines what is meaningful and what not, how a particular form should be used, etc. - Is invented to suit experience and then made independent of experience (pp. 43). "In mathematics we have propositions which contain the same symbols as, for example, "write down the integral of..", etc., with the difference that when we have a mathemaitical proposition time doesn't enter into it and in the other it does. Now this is not a metaphisical statement." (pp 34).
H. Freudenthal. Educational Studies in Mathematics, 1 (1/2):
3-8(Mai 1968)Systematization is a great virtue of mathematics, and if possible, the student has to learn this virtue, too. But then I mean the activity of systematizing, not its result. Its result is a system, a beautiful closed system, closed, with no entrance and no exit. In its highest perfection it can even be handled by a machine. But for what can be performed by machines, we need no humans. What humans have to learn is not mathematics as a closed system, but rather as an activity, the process of mathematizing reality and if possible even that of mathematizing mathematics..