A systematical exposition of the concept of number cannot be found in Aquinas’ works. Nevertheless, there are many places where the problem is touched. The problem is encountered on the one hand within the discussion of the category of quantity and on the other hand when Aquinas speaks about transcendental concepts and deals with the problem of numerical statements concerning God. The aim of the paper is to reconstruct, on the basis of Aquinas more or less fragmentary ideas, his concept (...) of number. (shrink)