The influence of Spengler on Wittgenstein's philosophical development is considered. The point of interest is in a significant methodological restructuring which it appears to have produced. After an initial over-enthusiastic reception, Wittgenstein is seen to object on some points which he attempted to emend in his own philosophy. Spengler's name disappeared inreworked manuscripts but traces persist in the Philosophical Investigations and an important section (§89-133) is found to be connected with it.