Can Descartes be certain that God would not allow an evil demon or computer to systematically deceive humanity?

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.

“Get 15% discount on your first 3 orders with us”
Use the following coupon
FIRST15

Order Now