He was a founding member of the Ten American Painters and taught at the Art Students League of New York.

Thomas was born in Boston, Massachusetts to parents Sophronia Durant and Paul Dewing, and served as a lithographic apprentice until at least 1870 when he was 19 years old.

"There he learned an academic technique; the careful delineation of volumetric form and meticulous but subtle evocation of texture were to be constant features of his work.

[3] He began teaching at the Art Students League of New York in 1881, the same year he married Maria Oakley.

Dewing's preferred vehicle of artistic expression is the refined, aristocratic female figure[3] situated in a moody and dreamlike surrounding.

[10] Often seated playing instruments, writing letters, or simply communicating with one another, Dewing's sensitively portrayed figures have a detachment from the viewer that keeps the spectator a remote witness to the scene rather than a participant.