 While Descartes defends ontological dualism, thus accepting the existence of a material world (res extensa) as well as immaterial minds (res cogitans) and God, Berkeley denies the existence of matter but not minds, of which God is one.One of the most fundamental debates in philosophy concerns the "true" nature of the world—whether it is some ethereal plane of ideas or a reality of atomic particles and energy.Materialism posits a real 'world out there,' as well as in and through us, that can be sensed—seen, heard, tasted, touched and felt, sometimes with prosthetic technologies corresponding to human sensing organs.