Zen is the latest Japanese development in a number of similar Buddhist traditions known as "Chan" in China, "Seon" in Korea, and "Thiên" in Vietnam, all supposedly having origins in India. It is an open question whether there is a sufficient degree of homogeneity to label this multifarious tradition "Chan" or "Zen." A safe alternative would be to treat each of the regional variations as distinct traditions, or even to handle the numerous subcategories in each of the East Asian regions as not necessarily connected with each other, at least not in the sense of a historical continuity.

One factor that makes these traditions especially complex is their emergence at various times and in various settings without being submitted to a central religious authority that would have defined their identity, their doctrine, and their structure as a religious unity. The multifarious nature of...