<P> "What is it like to be a bat?" is a paper by American philosopher Thomas Nagel, first published in The Philosophical Review in October 1974, and later in Nagel's Mortal Questions (1979). In it, Nagel argues that materialist theories of mind omit the essential component of consciousness, namely that there is something that it is (or feels) like to be a particular, conscious thing . He argues that an organism has conscious mental states, "if and only if there is something that it is like to be that organism--something it is like for the organism to be itself ." Daniel Dennett, a critic of Nagel's argument, nevertheless called this paper "the most widely cited and influential thought experiment about consciousness ." </P> <P> The thesis attempts to refute reductionism (the philosophical position that a complex system is nothing more than the sum of its parts). For example, a physicalist reductionist's approach to the mind--body problem holds that the mental process humans experience as consciousness can be fully described via physical processes in the brain and body . </P> <P> Nagel begins by arguing that the conscious experience is widespread, present in many animals (particularly mammals), and that for an organism to have a conscious experience it must be special, in the sense that its qualia or "subjective character of experience" are unique . Nagel stated, "An organism has conscious mental states if and only if there is something that it is like to be that organism--something that it is like for the organism to be itself ." </P>

Thomas nagel what it's like to be a bat summary