Buddhism, originating in India in the 5th century BCE and spreading to East Asia by the 2nd century CE, centers on continual self-analysis over ritual, sharing with other Eastern religions a worldview of an endless cycle of rebirth. Its arrival profoundly influenced Taoism, an ancient Chinese philosophy dating back to the 7th century BC, compelling it to restructure into a more organized religion and inspiring advancements in Chinese medicine through their competition. While Buddhism offered elaborate cosmology, Taoism focused on the all-encompassing "Tao"; their ideological crossover is particularly evident in Chan Buddhism, which adopted Taoist simplicity and emphasis on practical absorption.

This intertwined relationship led to extensive syncretism, where deities were mutually adopted: for example, the Buddhist Bodhisattva Marici became associated with the Taoist goddess Doumu, and the Taoist god Guan Yu was famously venerated as the Buddhist Sangharama Bodhisattva following a legendary encounter in 592 CE. Such profound exchanges, including the influence of Taoist concepts like the Lo Shu Square on Buddhist mandalas, highlight the dynamic and complex interactions that shaped these traditions over centuries.