Nagel on What It Is Like to Be a Bat

Quote

"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." — Thomas Nagel, "What Is It Like to Be a Bat?" (1974)

Historical Context

Thomas Nagel published "What Is It Like to Be a Bat?" in The Philosophical Review in 1974, at a moment when the philosophy of mind was dominated by physicalism. Identity theory and functionalism promised to reduce consciousness to brain states or information-processing roles, and many philosophers believed the mind-body problem was nearly solved. Nagel, then a young professor at Princeton, interrupted this optimism with a short paper that became one of the most cited in twentieth-century philosophy. The article grew out of his resistance to reductionist ambitions: he argued that any purely objective account of the brain leaves out the subjective character of experience. The paper introduced the phrase "what it is like" into the technical vocabulary of the field, and it shaped the debate over consciousness for the next fifty years. The quotation appears early in the paper, where Nagel defines conscious mental states in terms of the felt character of experience. It is not presented as a discovery but as a reminder of the datum any theory of mind must accommodate.

Philosophical Interpretation

Nagel's definitional sentence does two things. First, it ties consciousness to subjectivity: a mental state is conscious just in case there is a way that state feels from the inside. Second, it uses the bat as a thought experiment. Bats perceive the world through echolocation, a sensory modality entirely alien to us; we can study their neurophysiology completely yet never know what it is like to be a bat. Nagel's point is that physical facts do not exhaust the facts: there are truths about experience that only a first-person perspective can grasp. This is why reductionism fails. A reduction explains the objective in terms of the objective, but consciousness has an irreducibly subjective component. Nagel does not claim that a bat's experience is ineffable, only that the subjective point of view cannot be captured by third-person description. The argument anticipates the later "explanatory gap" and remains the standard statement of why consciousness resists scientific reduction. It also connects to qualia: the felt qualities of experience such as the redness of red or the painfulness of pain.

Related Concepts

The quotation belongs to the cluster of ideas explored in consciousness and the philosophy of mind. It introduces subjective experience as the central datum of the field and connects directly to qualia, the phenomenal character of mental states. It prefigures the hard problem of consciousness, the question of why physical processing gives rise to inner life, and the notion of the explanatory gap between physical and phenomenal facts. It also underlies what is it like to be a bat, the thought experiment that has become a touchstone of debates over physicalism, and it relates to Mary's room, a parallel argument about color experience. Reading Nagel is the natural first step toward understanding why many philosophers think consciousness cannot be fully explained by the objective methods of science.

Learning Path

Begin with the full text of "What Is It Like to Be a Bat?" (reprinted in Mortal Questions), then turn to David Chalmers on the hard problem and the explanatory gap. Contrast Nagel's view with Daniel Dennett, who argues the subjective character of experience is an illusion generated by the brain's self-modeling. Explore the knowledge argument in Mary's room, then test Nagel's claims against the empirical science of perception in the philosophy of neuroscience. For the wider tradition, compare Nagel's subjectivity with the introspective psychology of William James and the phenomenology of embodied experience.