Liam Dieghan was a major Human philosopher of the early 22nd century 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 and learned under her gentler tutelage" following the turmoil of World War III. (TNG: "Up The Long Ladder")

This character was only mentioned in dialogue.
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