He entered the profession of the law, and became in succession advocate to the general council of Artois, procureur to the parlement of Douai, master of requests, then intendant of Metz (1768) and of Lille (1774).
Having lost his first employment - with a procureur - through dishonesty, he obtained a clerkship in the Paris octroi in 1789, but was dismissed for abandoning his post when the Parisians burned the octroi barriers on the night of the L2th-13th of July 1789.
He was one of the leaders of the emeutes of the 20th of June and the 10th of August 1792, played an important part in the formation of the revolutionary commune which assured the success of the latter coup, and was made procureur of the commune.
During the session of the Legislative Assembly he exercised the functions of procureur syndic and was subsequently secretary-general of the department of Haut-Rhin.
Originally a procureur attached to the Chatelet at Paris, he sold his office in 1783, and became a clerk under the lieutenant-general of police.
In 1790 he became procureur of the Commune, and in July 1791 was elected by the newly created department of the Gironde a member of the court of appeal.
They owed their position to Anaxagoras Chaumette, procureur of the Commune, and to the fact that Simon had prevented one of the attempts of the baron de Batz.
He entered the magistracy and became procureur general at Grenoble, but resigned this office on the restoration of the Bourbons.