Descartes

In Rene Descartes Meditation V, he distinguishes the existence of God, believing he must prove that god exists before he can examine any corporeal objects outside of himself. By proving that the existence of God is not a sophism, he also argues that God is therefore the Supreme Being and the omnipotent one. His conclusion that God does exist enables him to prove the existence of material things, and the difference between the soul and …

…something more perfect or better than itself, and that we are less perfect than God therefore we could not have created God. So, this proves the existence of God and an external world. In my opinion Descartes has successfully proven the existence of God as well as one can because he started from the beginning and logically found a true foundation of beliefs and from there proved the existence of God and an external world.