On Peirce’s Discovery of Cantor’s Theorem1

Abstract

In 1897 C.S. Peirce published a proof of what is now known as Cantor’s Theorem. Though Peirce always claimed credit for discovery of this result, Cantor had published a proof of it in 1891, in a paper of which Peirce is known to have had a copy. I argue that Peirce’s discovery took place in 1896 and was indeed independent, though it was stimulated by the definition of cardinal exponentiation that Cantor first published in 1895.