Descartes assumes that it is reliable, when searching for true knowledge, to conclude that any principle that is obtained from our senses is false. His doubts are furthered by the deception of the content of our dreams, which is assembled and often mimics features we encounter throughout our lives. It is possible that our perceptions in which we establish a belief on was conjured while dreaming. However there are certain truths in sciences that whether asleep or awake are constantly genuine so in order to completely start at a base point in our beliefs must also take in the role of an omnipotent creator.
Descartes deploys more powerful skeptical hypotheses which call into question his claims to knowledge derived from these faculties. A method is a procedure for doing something which is repeated. Descartes method of doubt, then, is to deploy a skeptical hypothesis, see what can and what cannot be doubted on that hypothesis and then if there is something which can be doubted, to deploy a still stronger skeptical hypothesis to see if that which could not be doubted on the earlier hypothesis can be called into question by a stronger skeptical hypothesis. Descartes demonstrates that he is moving from one faculty to another, from the senses through the imagination to reason. Each of these faculties is the source of a whole vast set of propositions which one might claim to know. Each skeptical hypothesis acts like a sieve, some things it will not allow through — these are the things which can be doubted on that hypothesis, and while others it allows passing those things which cannot be doubted on that hypothesis.
Thus as each skeptical hypothesis is found to leave something which cannot be doubted, a new and more powerful skeptical hypothesis is deployed to try to bring those things which formerly could not be doubted into doubt. Since those things which can be doubted are studied by various crafts and sciences, these sciences themselves are called into doubt as Descartes proceeds. Descartes finds a truth, the truth that while he exists he cannot be deceived into thinking that he does not, which cannot be doubted on the most powerful of skeptical hypotheses ever deployed — the Evil Genius hypothesis.
In conclusion Descartes skeptical hypothesis is that our senses hypothesis tricks us at a distance, our dream hypothesis gives us imaginations and our Evil genius hypothesis gives us cause.
Broughton, J. “Descartes method of doubt” Princeton New Jersey: Princeton University Press.
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