The "Tao Te Ching" or "Taodejing" is widely considered the most influential Taoist text. According to legend, it was written by Lao Tzu, and often the book is simply referred to as the "Lao Tzu." However, authorship, precise date of origin, and even unity of the text are still subject of debate, and will probably never be known with certainty. The earliest texts of the "Tao Te Ching" that have been excavated (written on bamboo tablets) date back to the late 4th century BCE. Throughout the history of religious Taoism, the "Tao Te Ching" has been used as a ritual text.