[1] Born in Herstal in the Province of Liège, Janson studied philosophy and law at the Free University of Brussels.

From an early age he was a strong supporter of electoral reform and stood on the progressive wing of the Belgian liberal movement.

A modern study suggests that only "his visceral rejection of the class struggle" kept him from the burgeoning socialist movement.

Re-elected in 1889, he continued to agitate for universal suffrage, having established the Fédération progressiste of liberals who shared this, and other progressive goals.

Universal male suffrage, albeit with plural vote, was introduced following a general strike in 1893.