This article examines the essence-existence distinction in Spinoza's theory of modes. This distinction is commonly made in two ways. First, essence and existence are separated by cause. Essences are understood to follow vertically from the essence of God, while existence follows horizontally from other modes. I present textual and systematic arguments against such a causal bifurcation. Second, essence and existence are distinguished by their temporal nature. Essence is eternal. Existence is durational. However, in several passages, Spinoza writes that eternity and duration constitute two ways of understanding nature rather than two really distinct aspects of nature.