Part 1 of Essay
How can we know if we are a brain in a vat? Can we be sure that we are not the playthings of evil demons? These questions have been discussed by many philosophers in the past and still we do not have a proof that we are not some demon’s plaything. Yet, at least two prominent philosophers, René Descartes and John Locke beli ....

Part 2 of Essay
.... what God is should conform to that idea. Thus he wrote, the idea must be a "clear and distinct" perception of the mind. Nothing could make him doubt it. Furthermore, in Discourse on the method, Descartes introduced the famous Latin phrase “cogito ergo sum”, which means “I think, therefore I am.” Descartes then argued that “cogito ergo sum” has passed the test for “method of doubt ” because he can not be mistaken in his beliefs about the way things seem to him. Descartes held that by means of reason alone, certai ....