From the earliest period of his religious studies, Buddhadasa utilized a comparative approach and sought to be able to explain "Buddhist's teachings through other doctrines such as Tao, Hinduism, Christianity, Islam and Natural Science."[7] Through such a methodology he came to adopt a religious world-view that rejected exclusionary religious identification. In his No Religion (1993) Buddhadasa famously remarked, "in advanced perspectives there is no religious identification whatsoever."[8]
...those who have penetrated to the highest understanding will feel that the thing called 'religion' doesn't exist after all. There is no Buddhism; there is no Christianity; there is no Islam. How can they be the same or in conflict when they don't even exist?[9]
Religious scholar D.K. Swearer has compared Buddhadasa to the early Indian philosopher