James B. Nation, a mathematics professor, has earned a truly international reputation for the depth of his insight into lattice theory.

Mathematicians gain fame by solving well-known open problems whose difficulty has left them unresolved for many years, by opening up important new areas of research, or by breakthrough advances in well-established areas. Nation has managed to do all three. He created the field of congruence varieties, now regarded as a central part of lattice theory and universal algebra. Nation went on to one of his most famous feats, the solution of the Jónsson conjecture; he was able to prove the correctness of an elegant characterization of the class of free lattices. This problem had defied the efforts of the lattice theory community for approximately 20 years. Another 20-year-old problem, the finite height conjecture, was his next remarkable achievement. Here Nation astonished the mathematical world by showing the conjecture, almost universally believed true, was in fact, false.

Nation’s contributions have had significant impact, not only in the broad area of mathematics, but also in such areas as theoretical computer science.