Rene Descartes (1596 - 1650) was not only a philosopher but also a mathematician and scientist. As a philosopher he used the notion of scepticism as a means to find truth stripped of all ambiguity. In 'meditations one: what can be called into doubt' Descartes states that he shall "doubt everything that can possibly be doubted"1 in order to build a belief system which is indubitable. Descartes attempts to ascertain which of his opinions are false, not …showed first 75 words of 1850 total…

…showed last 75 words of 1850 total…able to tell if we are asleep and so the argument from dreams is inconsequential. The problem with such a theory is that we have no criterion by which we can test it. All this seems have achieved is to set a new challenge, to prove this theory as opposed to disproving Descartes'. In conclusion, it would appear that there are "no conclusive means by which one can distinguish between being awake and being asleep"1.