One of the early Taoist sages, the book that bears his name is likely an anthology written centuries after his death. Like Lao Tzu before him, even his existence is doubtful. Lieh Tzu may have lived in the fifth century BCE. The Chinese title of the book attributed to Lieh Tzu is Ch'ung-hsu Chih-te Chen-Ching or The Pure Classic of the Perfect Virtue of Simplicity and Vacuity.