Descartes believes that Almighty God could have distorted our perception of mathematics. “I will therefore assume that it is not God, who is supremely good and the source of truth, but rather a malevolent demon, extremely powerful and cunning, who has used all his energies to deceive me” (First Meditation, 5). Descartes assumes that it is not God but an evil demon who is committed to deceiving Descartes, so that everything Descartes perceives through his senses that he now knows is false. By doubting everything, Descartes can be sure that he will not be misled by this demon making his mind a better source of knowledge. "I see that without any effort I have finally arrived where I wanted. I know now that even bodies are not strictly perceived by the senses or the faculty of imagination but by the intellect alone, and that this perception does not derive of their being. understood; and in view of this, I know clearly that I can achieve an easier and more evident perception of my own mind than of anything else” (Second Meditation, 13). possible that all knowledge of external objects, including one's body, was deceptive due to the actions of an evil demon. However, it could not be possible that I was deceived about my presence or my nature as a rational person..