What do blindness, deafness, and mental retardation have in common? Are they best treated as physiological "defects" or as "inferiority complexes"? Does the social dimension introduced by Marxism change the way these questions can be posed--and alter the answers? The young Soviet psychologist L.S. Vygotsky sets out to answer all of these questions, and what he discovers leads him to places where today's "disability studies" and "special education"--critical or otherwise--have yet to follow.