EN
At the end of his life Gottlob Frege made his last attempt to ground mathematics. An essential role in this unfinished project was given to the analysis of the sources of knowledge. This last attempt reveals Frege's epistemological views. First of all, it shows the scope and the direction of changes his views took in comparison with Kant's conception. Besides, it allows us to see exactly what views Frege held at the end of his life. The unfinished character of Frege's attempt invites a continuation of this way of grounding mathematics.