Domat closely sympathized with the Port-Royalists, and on Pascal's death he was entrusted with the latter's private papers.

He is principally known from his elaborate legal digest, in three quarto volumes, under the title of Lois civiles dans leur ordre naturel (1689, with 68 later editions), an undertaking for which Louis XIV settled on him a pension of 2,000 livres.

After Hugo Doneau's more thorough but less consistent Commentarii iuris civilis (1589), the work was the first of this type of pan-European significance.

Domat's work was in line with earlier Humanist attempts to transform the seemingly random historical sources of law into a rational system of rules.

However, as a supporter of a Cartesian juridical order, Domat endeavoured to found all law upon ethical or religious principles, his motto being "L'homme est fait par Dieu et pour Dieu"[2] ("Man was made by God and for God").