Morin was born in Villefranche-en-Beaujolais and died in Paris. After studying philosophy in Aix and receiving a doctorate from Avignon in 1613, he became physician and astrologer and, ultimately, professor of mathematics at the Collège de France (1629–56). Early on, Morin went to Hungary and Transylvania to inspect mines. As a result of his trip, he wrote a short treatise, Nova Mundi sublunaris anatomia (1619), in which he argued for a new theory of the earth's “anatomy.” In 1623 he published Astrologicarum domorum cabala detecta, an argument for the twelve houses of the Zodiac based mainly on Cabalistic and numerological principles. Morin also made a name for himself with a number of astrological predictions, some of which were borne out.

In 1624 Morin distributed a pamphlet defending Aristotle against some atomist and alchemical theses. Though not a rigid Aristotelian, he also attacked the Copernican opinion of the earth's motion (De Telluris motu, 1631; Responsio pro Telluris quiete, 1634) (see earth, motion of the). He became involved in further polemics when he published his solution to the problem of determining longitude, rejected by Richelieu's experts. He also wrote circulars attacking Pierre Gassendi. Morin's principal work was Astrologia Gallica (1661), though he was also known for a short treatise on God, Quod Deus sit (1635), which consisted of a proof for the existence of God given in a geometrical fashion (using definitions, axioms, and theorems).

Descartes knew Morin, and they exchanged letters. Descartes sent a copy of the Discourse on Method to him, and this precipitated another exchange between them in which Morin articulated criticisms of Descartes’ theory of light. After a few letters, however, Descartes cut off the correspondence. Descartes also read Quod Deus sit when Mersenne sent it to him, but indicated his dissatisfaction with the work in a letter written shortly before the publication of the Meditations: “I have read through Mr. Morin's booklet. Its chief defect is that he treats of the infinite everywhere as if his mind were above it and he could comprehend its properties. That is a common fault with nearly everyone…. And thus all that he says right up to the end is far removed from the geometrical evidence and certitude that he would seem to be promising at the beginning” (AT III 293–94, CSMK 171–72).