Gaisi Takeuti was born on January 25, 1926, and died on May 10, 2017.

He was a Japanese mathematician.

He was known for his work in proof theory.

Following his graduation from Tokyo University, he went to Princeton to study under Kurt Gödel.

Gaisi later became a professor at the University of Illinois at Urbana-Champaign.

He was president (2003–2009) of the Kurt Gödel Society, having worked on the respected book Memoirs of a Proof Theorist: Godel and Other Logicians.

Takeuti’s goal was to prove the consistency of the real numbers.

Even now, Takeuti’s conjecture speculates that a sequent formalization of second-order logic has cut-elimination.

Takeuti was also known for his work on ordinal diagrams with Akiko Kino.

Gaisi Takeuti passed away at 91 years old.