Only those beliefs that are absolutely certain, in the strongest sense of the term, will survive Descartes' test, and only such beliefs, he holds, can serve as truly reliable foundations for science. .
Now when you look out your window you see what you expect to be seen, the road, sidewalk, streetlight, trees, and etc only with suspending your beliefs can you realize that, are you absolutely sure of what you see out the window is what you see? This is how Descartes viewed the world, and how he approached science and knowledge.
The question now asked is: "Do you believe in reality?- I answer this question thusly: " I believe in this reality that is presented to me, by the world or whatever Greater Power or Being. Yet I also believe that there are other realties that I can not see, hear or touch, so does that make this one I can see real or not real?- According to Descartes, we justify many of our opinions with information collected through our senses of sight, hearing, touch, smell and taste. For instance, I believe that my roommate Chris is home from work if I see the headlights flash in the window, and the time is 1:00 AM and I see a figure walking up to the door, however as Descartes notes, "From time to time I have found that senses deceive."" By this rule then, it may not be my roommate Chris, it could be a different friend, or even worse it could be a burglar or mass-murder, all depending on what we see and believe. Continuing this exercise, Descartes then suggests that even such relatively uncontroversial beliefs as that all of you are sitting here listening to my presentation is subject to doubt. However, Descartes points out that we often make mistakes about precisely these kinds of things when we dream. When you are dreaming, it may seem to you that you are sitting in your chair, reading, when in fact you are fast asleep in your bed (Descartes, pp. 12-13). We are unable to distinguish waking exp-erience from experiences of the sort we appear to have in dreams until after we wake up, a notion Morpheus affirms as he asks:.
