Descartes finds a conflict between true ideas and false ideas - there is no way to tell them apart. God is implied fomr things having perfect existence Descartes' argument is similar to Anzelm and Spinoza - the existence of the notion of perfection implies God. Plato would say wax has an essence that makes it wax - all wax tries to approximate the essence of ideal wax. Modern chemistry can explain wax as an arrangement of molecules. Absolutes exist as concepts.
Absolute evil is the inverse of perfection and thus, non-existent.
Existence is neutral. Perfection and imperfection are independent of neutrality. If God does not exist, then we'll have to invent him. Descartes proves the existence of a real world by saying that God is not deceiving - deceiving is not perfection.