Robert Lawson Vaught

American mathematical logician and one of the founders of model theory, known for the Tarski–Vaught test for elementary substructures, the Feferman–Vaught theorem, the Łoś–Vaught test for completeness and decidability, the Vaught two-cardinal theorem, and his conjecture on the nonfinite axiomatizability of totally categorical theories (this work eventually led to geometric stability theory).

Vaught was a musical prodigy in his youth, in his case playing the piano. He began his university studies at Pomona College at age 16. When World War II broke out, he enlisted into the US Navy, which assigned him to the University of California's V-12 program. He graduated in 1945 with an AB in physics.

In 1946, he began a Ph.D. in mathematics at Berkeley. He initially worked under the supervision of the topologist John L. Kelley, writing on C* algebras. In 1950, in response to McCarthyite pressures, Berkeley required all staff to sign a loyalty oath. Kelley declined and moved his career to Tulane University for three years. Vaught then began afresh under the supervision of Alfred Tarski, completing in 1954 a thesis on mathematical logic, "Topics in the Theory of Arithmetical Classes and Boolean Algebras." After spending four years at the University of Washington, Vaught returned to Berkeley in 1958, where he remained until his 1991 retirement.

In 1957, Vaught married Marilyn Maca; they had two children. He died on 2 April 2002 at age 75 in Berkeley, California.