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, PhD had real life experience to help him in his best known roles.
reason: Don SInclair Davis, PhD was in the military, and his best known roles are that of men in the military, so he was able to draw from his experience in the military to channel Major Briggs and later General Hammond, both of whom are military characters themselves.