- Next, I carefully examined what I was. I realized that I could imagine having no body and that there was no world or place where I might be. However, I couldn’t suppose that I didn’t exist. On the contrary, the very act of doubting the truth of other things made it clear and certain that I did exist. If I had stopped thinking, even if all the other things I had imagined were real, I would have no reason to believe I existed. From this, I concluded that I am a substance whose entire essence or nature is just thinking. I don’t need a place to exist, nor am I dependent on anything material. Thus, “I”—that is, the mind by which I am what I am—is completely distinct from the body. The mind is even more easily known than the body and would continue to exist even if the body did not.