Liam Dieghan

From Memory Alpha, the free Star Trek reference

Liam Dieghan was an early 22nd century human philosopher from Earth who founded the Neo-transcendentalist movement. Lieutenant Commander Data had observed in 2365 that Mr. Dieghan had advocated "a simpler life in which one lived in harmony with nature" following the turmoil of World War III (TNG: "Up The Long Ladder").

The period of turbulence noted by Data may have been a reference to the post-atomic horror.