Descartes' Meditation One Being a foundationalist, Descartes needs to destroy the foundations of his beliefs so that in his Meditations he will be able to build upon new foundations of undeniable and self evident truths. In order to do this Descartes must first find a valid argument that will allow him to doubt his foundation beliefs and in turn doubt what is considered to be reality. He begins by first noting that one can not trust their own senses, because we can be deceived by our sciences. An example of such would be if one looks at an optical illusion, they are seeing something that is not really there, and therefore a