For a moment assume that Descartes’ argument works in proving God’s existence, does the ultimate conclusion follow as stated in premise 6? Can Descartes be certain that God would not allow an evil demon or computer to systematically deceive humanity? Maybe God has a reason, or needs to teach humanity a lesson.
Descartes’ argument for the existence of God relies on the idea that there must be a cause for the clear and distinct ideas in our minds. He posits that this cause must be a perfect, non-deceiving being, which he calls God. However, as you point out, it is possible that God could have reasons for allowing deception, such as teaching humanity a lesson. This would call into question the conclusion that the cause of our clear and distinct ideas is a non-deceiving being. Additionally, Descartes does not address the possibility of an evil demon or computer deceiving humanity, so it is unclear how his argument would address this possibility.