Xuantong 玄同 (tentatively translated as dark oneness) is a unique Daoist idea that represents an ideally mental and physical state as a result of cultivation. However, owing to limited context in the Laozi, there is no consensus on the interpretation of xuantong. Contemporary studies have also neglected xuantong’s evolution in early texts and assumed a homogeneous understanding, and hence, failed to provide a nuanced account. In this article, I investigate how xuantong evolves from the Guodian Laozi to the Huainanzi and (...) Wenzi. I argue that although xuantong may originate from the Laozi, it is in the Wenzi that a coherent theory of xuantong is accomplished. This theory advocates an orderly process of cultivation that covers internal mental states, external acts, and integration with the whole universe. The cultivation would eventually lead people to adopt an undifferentiated perspective on, and reach oneness with, all things in the universe. (shrink)