This thesis deals with the philosophical basis behind Wittgenstein`s proposals in the philosophy of mathematics. We try to show that there is a semantic core from which these proposals are derived: the idea that the meaning of a sentence should be taken to be its truth conditions. We sort out this insight from its inception in Frege through the Tractatus all the way to the last phase of Wittgenstein`s thought. In our last two chapters we discuss the changes this approach went through in this last phase of the philosopher`s thought in relation to the idea of triangularization of the underlying semantics. We then deal in some detail with Wittgenstein`s proposed interpretation of some types of elementary mathematical propositions, especially arithmetical propositions.