This study explores the inner world of a rare human phenomenon—a man who was endowed with virtually limitless powers of memory. From his intimate knowledge of S., the mnemonist, gained from conversations and testing over a period of almost thirty years, A. R. Luria is able to reveal in rich detail not only the obvious strengths of S.’s astonishing memory but also his surprising weaknesses: his crippling inability to forget, his pattern of reacting passively to life, and his uniquely handicapped personality.