Comment by mLuby

This is unfortunately a widespread interpretation of Wittgenstien's philosophy of mathematics, but it is not a very charitable reading.

Wittgenstein emphasised on numerous occasions (for example directly at the beginning of his lectures on the foundations of mathematics in 1939) that his interest in these proofs was _philosophical_ and that he never intended to criticise any of them _on mathematical grounds_. He explicitly said that his aim was not to interfere with mathematicians, but to investigate the _philosophical conclusions_ drawn by these mathematicians from their proofs.

What exactly Wittgenstein found problematic is hard to describe in a short comment, because much of it depends on Wittgenstein's view of philosophy as a whole, but one example is the platonist bent of Gödel's theorem and his conviction that there are some mathematical "facts" that can never be discovered by mathematical reason. Wittgenstein wants to ask what it means to say that something is "intuitively true", but not provable in any consistent system, but he does not want to object to Gödel's results, merely its "standing".

In Cantor's case Wittgenstein is interested in the concept of the transfinite and of infinities "bigger" than other infinities. He does not object to Cantor's proof at all, but regards the philosophical conclusions drawn from it with suspicion.

(One good example of a philosophical abuse of Gödel's theorem is the argument that computers will never be able to think like humans, because Gödel's theorem demonstrates a limit to what any computer can do as a formal system, but we humans can nevertheless grasp the unprovable statements as intuitively true. This is basically the argument by J. R. Lucas. This is the kind of philosophical nonsense that Wittgenstein wanted to attack and his position on these matters is coincidentally quite similar to Turing's position, who was a student of Wittgenstein's lectures on the foundations of mathematics.)

It certainly did not help that the so-called Remarks on the Foundations of Mathematics are in some parts highly selective constructions by the editors of his posthumous writings.

tl;dr: it's complicated. Wittgenstein never objected to the mathematical results by Gödel and Cantor, but he thought that their results were often blown out of proportion by shoddy philosophical conclusions made on the basis of these perfectly fine mathematical arguments.

In general, Wittgenstein wasn't exactly a mathematician...

Can you say more of either of these? Especially the diagonalization argument which seems difficult to, er, argue with.

Unless he published a formal demonstration of Gödel's 'error', Wittengenstein's belief is of mere biographical interest. History is littered with eminent people who had all sorts of erroneous beliefs about theories and ideas that we now see as having withstood the test of time.

Maybe. On the other hand, that period saw incredible technological and societal progress. Thiel called it the period of "definite [technological] optimism." https://archive.org/details/ZeroToOneByPeterThiel/page/n47