Gaisi Takeuti (竹内 外史 Takeuchi Gaishi, born January 25, 1926) is a Japanese mathematician, known for his work in proof theory.
After graduating from Tokyo University, he went to Princeton to study under Kurt Gödel. He later became a professor at the University of Illinois at Urbana-Champaign. Takeuti was president (2003-2009) of the Kurt Gödel Society, having worked on the respected book Memoirs of a Proof Theorist: Godel and Other Logicians. His goal was to prove the consistency of the real numbers. To this end, Takeuti's conjecture speculates that a sequent formalisation of second-order logic has cut-elimination. He is also known for his work on ordinal diagrams with Akiko Kino.
- ^ Takeuti, Gaisi (1953), "On a generalized logic calculus", Japanese Journal of Mathematics 23: 39–96, ISSN 0075-3432
An erratum to this article was published in the same journal (24:149–156, 1954).