The distinction between essence (essentia) and existence (existentia) plays a major role in Spinoza’s metaphysics. Although the distinction did not originate with Avicenna, it is primarily through Avicenna’s influence that it became widespread, if not ubiquitous, in both Jewish and Christian medieval philosophy (e.g., Ogden 2021). Spinoza was clearly familiar with this important distinction through his study of Maimonides, Crescas, and Descartes, and it is particularly useful to examine Spinoza’s employment of the distinction in contrast to Descartes’. In the Meditations, (...) Descartes relies on the distinction in a proof of God’s existence, and in his exploration of the essence of material things (both in Meditation Five). (shrink)