Summary. — Although studied very little, Albert Lautman has already been labelled a neo-platonist. Regarded as too speculative despite his exceptional mathematical erudition and his close relationship to Hilberfs axiomatic structuralism, his philosophy of mathematics has not been a subject of specific attention until now. And yet it is, in our opinion, of noteworthy importance. In separating from mathematical theories an additional level of reality lying above, level made up of dialectic- problematic ideas whose understanding is equivalent to the genesis of real theories in which they are determined and achieved, this philosophy of mathematics allows a (transcendental) doctrine of relationships between mathematics and reality to be develope...