“These are the fruits of W.’s style” – ...

It is well known that Karl Popper read Ludwig Wittgenstein’s Tractatus. Popper’s interpretation of Wittgenstein served as a blueprint for Popper’s criticism of language philosophy throughout his work. Apart from the allegation that Popper misunderstood Wittgenstein, one objection to Popper’s criticisms is that they exclusively refer to the Tractatus, which is assumed to be the only work of Wittgenstein that Popper ever read. This paper presents evidence that Popper read the notebooks of Wittgenstein. On notes found in his edition of George Spencer Brown’s Laws of Form, Popper addresses a problem of negation that Wittgenstein was concerned with in 1915, and suggests that Spencer-Brown accomplished what Wittgenstein was aiming for.