A 50th anniversary edition of one of the most widely influential articles of 20th Century philosophy nConsciousness is what makes the mind-body problem really intractable. So begins Thomas Nagels classic 1974 essay What is it Like to be a Bat? Nagels essay initiated the now widespread attention to consciousness as a central problem for philosophy, psychology, and neuroscience; it also influenced the recognition of the consciousness of nonhuman creatures as an important subject of study. Nagel argued that the essential subjectivity of conscious experience--what it is like for the creature undergoing it--means that reductionist theories of mind, which attempt to analyze it in physical terms, can never 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. n nThis edition reissues this classic and widely influential article on its 50th anniversary, along with a new preface discussing the origins and influence of the essay, as well as Further Thoughts: The Psychophysical Nexus, a supplementary essay which describes Nagels later thoughts about how to respond to the problem posed by What Is It Like to Be a Bat? This second essay suggests that the most promising path forward for the mind-body problem, if one accepts the irreducible subjectivity of consciousness, is to seek a necessary connection between mental and neurophysiogical states through a more fundamental type of state which is neither mental nor physical but necessitates them both as essential aspects. In other words, a state that is physical from the outside and mental from the inside, just as we are. This would be a form of monism, requiring the formation of new concepts, since our present concepts of the mental and the physical do not entail such a necessary connection. The essay explains why the relation between the mental and the physical may be necessary, even though our present concepts make it appear contingent.n