Frege at a Crossroad

Claude Imbert

Not everything is gold, but there is gold in it. Such have been the words with which Frege transmitted a collection of his yet unpublished writings to his adopted son. Time has come to reappraise Frege’s achievement from a contemporary point of view. After sketching Frege’s mathematical formation at the Gaussian Königsberg University, I reconsider:

- The first Begriffsschrit ( 1879) as it has been reasessed by Gödel in his article on Russell’s Logic

- The second Begriffsschrift (1889), its motivations and its fatal contradiction. An episode we may qualify as the end of philosophical Galileism : from Descartes to Kant.

- Frege’s sideways: his last logical research , his considerations on the visual field and his long support from the Zeiss corporation

-Frege’s today: proof theory, information theory, languages and programs.

A conclusion will come back on Frege and Wittgenstein exchanges focusing on their impact today.