Descartes' metaphysical project revolves around the themes of the self, God, and the external world. He takes the self as a thinking substance by separating it from the extended substance. Unlike God - the uncreated substance - the self and the external world are considered to be created substances. This paper has three objectives. The first is to find out Descartes' answer to the question of what the self and the external world are by examining existence and persistence. The second is to show how Descartes demonstrates the self-getting access to this world. The last is to point out the deficiency in his metaphysical project, namely, the deficiency in his accounts of the self, the external world, and the relation between them. This paper attempts to make up for this deficiency by putting the missing piece, i.e., time into its place.