Can One Perceive Or Confirm The Existence Of An Idea Or Object That Is External "I think therefore I am." Man wills, refuses, perceives, understands, and denies many principles. As explained by Rene' Descartes, man is a thinking thing, a conscious being who truthfully exists because he is certain that it is so. All that man perceives is internally present and not external to him or his mind. The focal point of the third meditation that must be dealt with is: Can one perceive or confirm the existence of an idea or object that is external to h ....