Hence, any idea, insofar as it exists at all, has its share of truth. Descartes, Meditations 114.5, 116.5. Descartes, Meditations 97.5, 110.4, 121.5. This is the ontological argument for the existence of God. If a proposition's truth is possible, we may assume that it is actually true, and if an entity's existence is possible, we may assume that it actually exists, unless there are special reasons to think not.
Dependence is an imperfection.
Descartes, Discourse 27.3. Hence, the things in the middle of the chain are dependent or contingent. The being at the top of the chain is utterly independent or self-sufficient or absolute. Descartes, Meditations 104.3, 106.3. Therefore a cause must be more perfect than its effect.