evidently true, it’s not.

There is a distinction between the mind and the body. The mind is essentially thinking and the body is essentially extended so that the two have nothing in common. In Descartes’ Meditations on Philosophy, there is a character, the mediator, and he reasons that he might cast all the opinions of others into doubt if he can doubt the foundations of basic principles upon which his opinions are founded.

In the first meditation, Descartes rejects as if false any belief that is open to doubt. He pushes skepticism to its limits by introducing the notion of an “evil demon”, a being that always tricks us into believing true what is actually false. The only certainty that Descartes can find is that nothing is certain. Knowledge acquired through the senses was called into doubt by argument from dreaming and knowledge acquired through intellect was called into doubt by the evil demon argument.

In Descartes Meditation Two, Descartes comes up with the argument of God’s existence because he began to wonder something. He began to wonder if he exists. “I think, I exist.” He had previously concluded that the world, minds, bodies, etc. did not exists and then began to doubt the existence of himself. But, to have been able to doubt this and to have the “deceiver” deceive him into thinking that he does not exist, then he concludes that he must exist in order to have been deceived. Descartes argues that even assuming there is an evil spirit who constantly deceives me, it is certain that my own self exists: for the very notion of an evil spirit assumes that the spirit deceives someone; me. So even if constantly deceived, I can’t doubt that I exist. Descartes holds that the sentence “I exist” must be true whenever I think it to myself. I may utterly deceive as to what I believe but even the most radical doubt of all, which is doubting my own existence, must imply that I exist. He creates the phrase, “cogito ergo sum.” This means, I think therefore I am. So according