Abstract This essay is Thomas Nagel’s classic “What Is It Like to Be a Bat?,” which was influential in drawing attention to consciousness as a central problem for philosophy, psychology, and neuroscience. It also influenced the recognition of the consciousness of non-human creatures as an important subject of study. The essay argues that the essential subjectivity of conscious experience—what it is like for the creature undergoing it—means that reductionist theories of mind, which try to analyze it in physical terms, cannot succeed. It follows that the physical sciences cannot provide a complete description of reality, and that the physical conception of objective reality must be transcended if science is going to comprehend the mind.