gained more inner stability, he gradually headed towards Bangkok, consulting his childhood friend Chao Khun Upali on practices pertaining to the development of insight (Pali: paññā, also meaning "wisdom" or "discernment"). He then left for an unspecified period, staying in caves in Lopburi, before returning to Bangkok one final time to consult with Chao Khun Upali, again pertaining to the practice of paññā. Feeling confident in his paññā practice he left for Sarika Cave. During his stay there, Ajahn Mun was critically ill for several days. After medicines failed to remedy his illness, Ajahn Mun ceased to take medication and resolved to rely on the power of his Buddhist practice. Ajahn Mun investigated the nature of the mind and this pain, until his illness disappeared, and successfully coped with visions featuring a club-wielding demon apparition who claimed he was the owner of the cave. According to forest tradition accounts, Ajahn Mun attained the noble level of non-returner (Pali: "anagami") after subduing this apparition and working through subsequent visions he encountered in the cave. Establishment and resistance (1900s–1930s) Establishment Ajahn Mun returned to the Northeast to start teaching, which marked the effective beginning of the Kammatthana tradition. He insisted on a scrupulous observance of the Vinaya, the Buddhist monastic code, and of the protocols, the instructions for the daily activities of the monk. He taught that virtue was a matter of the mind, not of rituals, and that intention forms the essence of virtue, not the proper conduct of rituals. He asserted that meditative concentration was necessary on the Buddhist path, and that the practice of jhana and the experience of Nirvana was still possible even in modern times. Resistance Ajahn Mun's approach met with resistance from the religious establishment. He challenged the text-based approach of the city-monks, opposing their claims about the non-attainability of jhāna and nibbāna with his own experience-based teachings. His report of having reached a noble attainment was met with mixed reaction among the Thai clergy. The ecclesiastical official Ven. Chao Khun Upali held Ajahn Run in high esteem, which would be a significant factor in the subsequent leeway that state authorities gave him and his students. Tisso Uan (1867–1956), who later rose to Thailand's highest ecclesiastical rank of somdet, thoroughly rejected the authenticity of Ajahn Mun's attainment. Tension between the forest tradition and the Thammayut administrative hierarchy escalated in 1926 when Tisso Uan attempted to drive