All rights reserved. The paper aims to clarify the meaning of the well-known Cartesian thesis 'existence is a perfection.' Since Gassendi's objections, it has been traditionally interpreted as saying that existence, like extension, is a first-order property that determines things to be specifically such (either essentially or accidentally). But Descartes never accepted this interpretation and-the paper argues-the texts do not support it. On the other hand, some scholars who reject Gassendi's reading have not advanced a convincing alternative. This article seeks to provide such an alternative by analysing the thesis in its proper context, the Fifth Meditation. First, it expounds Descartes' notions of nature and perfection. Then, it argues- A gainst both traditional and alternative readings-that the thesis has a twofold meaning. Regarding any finite nature qua possible, it means that existence may determine it as a second-order property. Regarding the infinite nature qua possible, it means that existence determines it as an individual property.
- A priori proof