In the 5th Century BC, Prince Gautama belonged to the Shakya clan of northern India. At the age of 19, he escaped over the palace wall at midnight and fled to Mount Dandoku, where he shaved his head and spent the next six years engaged in harsh ascetic practices. Not finding the answer to his question, "Why is there suffering?," he sat beneath the Bodhi Tree and resolved to meditate until he realized his answer. Legend has it that while he sat, spiders spun webs between his eyebrows, birds took up residence in a nest on top of his head, and reeds grew up around him, but he sat erect and immovably still for six more years.
In his 30th year, on the 8th day of the 12th month, Gautama awakened to his true self and became Shakyamuni ("Jewel of the Shakya Clan") Buddha upon seeing the morning star, saying, "How marvelous! I, together with the whole of the great earth and all its sentient beings, have simultaneously realized enlightenment."
How could his realization have been shared simultaneously with all other sentient beings unless, in his enlightened state, he saw no distinction between his self and all other sentient beings? What if this loss of distinction between self and other was itself the enlightenment experience?
Later, he recalled, "When the bright star appeared, I together with all sentient beings attained the way." Zen Master Dogen notes (in Dharma Hall Discourse 37 of the Eihei Koroku, for those of you who care), "Originally there was no great way; however, today for the first time, old sage Shakyamuni appears. What is it he calls sentient beings, and what is it he calls the way, and its attainment? Speak immediately, speak immediately!"