The List of Hilbert’s Twenty-Three Problems: Hilbert’s Problem #15

Hilbert’s Fifteenth Problem is the igorous foundation of Schubert’s enumerative calculus.

Hilbert’s 15th problem is another question of rigor. He called for mathematicians to put Schubert’s enumerative calculus, a branch of mathematics dealing with counting problems in geometry, on a rigorous footing. Mathematicians have come a long way on this, though the problem is not completely resolved.