Premise: Don Sinclair Davis, PhD (August 4, 1942 – June 29, 2008) was an American character actor best-known for playing General Hammond in the television series "Stargate SG-1" (1997–2007), and earlier for playing Major Garland Briggs on the television series "Twin Peaks" (1990–1991). He was also a theater professor, painter, and United States Army captain.
Hypothesis: Don Sinclair Davis has assumed more than one professional role.