In Rene Descartes' Meditations on First Philosophy,
"First Meditation", Descartes hypothesizes the existence of an
omniscient, and malevolent being who is capable of
deceiving us with false beliefs. If such a being existed,
how could we ever know if the beliefs we hold at any given time were true? This is Descartes’ version of the
skeptical hypothesis which states that all of beliefs might be false.