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Mathematics/Wittgenstein: mathematical propositions are not true or false - but they show what is usefull and what useless.
See/Mathematics/Wittgenstein: E.g. that four consists of two and two in the sense of 2 + 2 = 4, cannot be seen. - There is no phenomenon of seeing that a grammatical sentence applies.
Calculate/Wittgenstein: that a calculation with different methods (for example, tally) leads to the same result, does not come from the nature of the process - from the processes follows no need.
Decimal fraction/development/Wittgenstein: (> decimals): the discovered periodicity is no reason that someone needs to accept that it always has to go on like this. - but he must well accept if he is not a fool. - The fact that we have to acknowledge that in mathematics two methods lead to the same result, is not a fact of experience, but a rule.
Evolution of the number π/Wittgenstein: question whether 3 sevens have to occur or do not have to occur - in fact there is no way to answer that. - It is weird that we can ask this question without knowing a means of discovering the answer. - ((s)> verificationism.) - Since π is our own creation, we could say that we have invented all the consequences.
Mathematics/Name/Object/Wittgenstein: in mathematics, there is no such thing as the description of something on the one hand, and his name on the other.
Sense/Mathematics/Wittgenstein: it is not that a mathematical proposition only makes sense if it was proven to be true or false, but first he must have sense, so that it can be true or false.
Definition Fundamental Theorem of Algebra/Wittgenstein: every equation has a solution.
Vorlesungen 1930-35 Frankfurt 1989
Das Blaue Buch - Eine Philosophische Betrachtung Frankfurt 1984
Tractatus Logico Philosophicus Frankfurt/M 1960