He was a follower of the Guesdist movement in the 1880s, and did much to raise awareness of Karl Marx's theories of the weaknesses of capitalism through his books and articles.

His uncle was Amédée Deville, vice-president of the Anatomical Society of Paris, who was proscribed after the coup d'état of 2 December 1851.

Gabriel Deville attended secondary school in Tarbes, then studied in the faculties of law in Toulouse and Paris, where he obtained his license as a lawyer.

Deville studied the works of Karl Marx, including the translation of Le Capital by Joseph Roy.

[3] Talking of his early years Deville wrote, "In 1877 when I was one of those who began to propagate the collectivist and Marxist theory by the newspaper, I scarcely knew the rudiments ... We learned socialism at the same time that we informed our readers, and it is incontestable that we sometimes made mistakes.

When both Guesde and Deville said they would challenge anyone who called them a coward to a duel, Marx told them the idiocy and immaturity of their comments was offensive.

[8] In the early 1890s Deville gradually withdrew from formal POF membership, although his work continued to show Guesdist influences.

[14] L'Ère Nouvelle hosted articles by Marxist thinkers from the various countries of Europe: primarily Friedrich Engels and Paul Lafargue, but also Georgi Plekhanov, Clara Zetkin, Karl Kautsky, Jean Jaurès, Gabriel Deville and Jules Guesde.

[17] On 21 June 1896 Deville was elected deputy for the first district of the 4th arrondissement of Paris in a by-election after Désiré Barodet(fr) had resigned.

[2][1] Around this time Jean Jaurès asked Deville to help him locate primary material on the French Revolution in the parliamentary archives.

Although Deville still took a theoretical interest in capitalism's economic and social problems, he had now become much closer to the independent socialists associated with Jaurès.

Babeuf gave a clear statement of egalitarian principles, but was also pragmatic and willing to support the Directory against the threat of royalist counter-revolution.

[2] Deville became a member of the Central Committee for Research and Publication of Documents on the Economic History of the French Revolution in December 1903.