Bodhidharma, the founder of Ch'an (Zen) Buddhism, was invited to visit the Emperor Wu of Liang, who was a great patron of Buddhism. The Emperor had built many monasteries, and he asked Bodhidharma what merit his generosity had earned. "No merit," said Bodhidharma. Startled, the Emperor asked Bodhidharma the supreme truth of the Dharma. "unholy emptiness" replied Bodhidharma. Finally, the Emperor asked, "Who are you?" "I don't know" said Bodhidharma.
Stephen Batchelor examines "Emptiness" in the context of the Buddha's teaching of the "Four Noble Truths".