Because God is perfect, He cannot deceive because all deception implies imperfection. Descartes writes, “And it seems to me that I now have before me a road which will lead us from the contemplation of the true God (in whom all the treasures of science and wisdom are contained) to the knowledge of the other objects of the universe” (19). God does not deceive nor has He given us any faculty which leads us into error. Descartes then ponders how error arises, if not from God.

Descartes asserts that errors depend on two causes, the faculty of knowledge within him and the power of choice or free will. Through understanding, one apprehends things and makes judgments upon them. While our understanding is limited, it is not the source of error, which arises instead through free will. Descartes writes,

It is free-will alone or liberty of choice which I find to be so great in me that I can conceive no other idea to be more great; it is indeed the case that it is for the most part this will that causes me to know that in some manner I bear the image and similitude of God (21).