Heidegger's most penetrating reflections on the essence of mathematical physics inevitably turn on the sense in which it is mathematical. And in a fashion which has come to be known as "Heideggerian," he bases his reflections on the original Greek sense of mathesis and mathemata, so that the notion of the "mathematical" is thereby broadened from its current reference to the "apriori" discipline that deals with number, quantity and the like, to the comprehensive sense of a process of learning in which we come to know what we already know, where the mathemata, what is thereby known, refers to any apriori knowledge whatsoever.