Following his return to Geneva in 1824, he was named chair of rational philosophy at the Academy, a position he maintained until 1847.As a student in Geneva, he came under the influence of Augustin Pyramus de Candolle, and in the process, developed a lifelong passion for botany.
He was a principal contributor towards Candolle's publication of "Prodromus Systematis Naturalis Regni Vegetabilis", being the author of the sections involving the plant families Marcgraviaceae, Convolvulaceae, Hydroleaceae, Selaginaceae, Nyctaginaceae, Hypericineae and Guttiferae.
The botanical genus Choisya (family Rutaceae) is named in his honor.As a theologian/philosopher he published works with titles such as, "Des doctrines exclusives en philosophie rationelle" (1828) and "Les lois morales: Fragment d'un cours de philosophie morale" (1836).