Descartes epistemology is known as foundationalism. In his Meditations, Descartes tries to discover certain, indubitable foundations for knowledge. He is searching for absolute certainty, and does this by subjecting everything to doubt. Through this he reaches the one thing he believes to be certain, his existence. In Meditation One, Descartes describes his method of doubt. He subjects all of his beliefs to the strongest of doubts. He invokes the notion of an all-powerful, evil demon who could be deceiving him in the realm of sensory perception, in his very understanding of matter and even in the simplest cases of mathematics such as in the equation 2+3=5.