Abstract:  Contrary to received opinion, Descartes’ view on the merits of the ontological proof may actually agree with that of Thomas Aquinas, whose rejection of the a priori existence proof has stocked the armories of anti-Anselmians ever since. In a rarely noted passage of the First Replies, Descartes claims not to differ in any respect from Thomas on the proof, a claim that gains sense in light of recent work on the Fifth Meditation. That work in turn reveals a well-founded, if surprising, understanding of the Cartesian proof and of Cartesianism's true relation to Thomism.