What is language? Can we distinguish language from general cognition? Is language an isolable, biologically coherent system? Does the linguistic description of language as an autonomous system, formed from a combination of more-or-less autonomous subsystems, correspond to psychological and neurophysiological fact? This collection of original contributions, drawn from a Neurosciences Research Program Work Session, provides a comprehensive and thoroughly up-to-date discussion of the research, knowledge, and debates in the neurobiology of language.