He was born from an old aristocratic family, studied first in a Jesuit college at Clermont, and then theology and philosophy at the Sorbonne of Paris. When he was 23 years old he joined the Congregation of the Oratory where he was above all engaged in educating the young. In 1657 he was ordained priest. He made friends with the Jansenist leader Antoine Arnauld in the seminary of Saint-Magloire, where Quesnel was deputy director and Arnauld had found his refuge. For the young’s education he published a brief manual on the Gospels in 1671. In 1675 pope Leo the Great’s Works edition by Quesnel was placed on the Index due to the Jansenist imprint of the included notes and dissertations. Quesnel’s more and more evident Jansenist sympathies led to his banishment from Paris in 1681, his exile to Orléans, and then, three years later, to his expulsion from the Oratory for his refusal to accept the anti-Jansenist decrees enacted in 1672 by the general de Sainte-Marthe. After his banishment from France (1684) Quesnel fled to Brussels where he took up abode with Arnauld; after the latter’s death (1694), Quesnel was regarded as the main leader of Jansenism. In 1703 he was arrested at Brussels, yet he soon fled to Amsterdam, where at the end he definitely settled the remainder of his life and died.