"Epistemology is the study of the nature and scope of knowledge and justified belief. It analyzes the nature of knowledge and how it relates to similar notions such as truth, belief and justification. It also deals with the means of production of knowledge, as well as skepticism about different knowledge claims."-wiki
Similarly, Christians and Muslim origin of knowledge and belief is Bible and Quran that is part of Jewish's Tanakh (Hebrew Bible).
Likewise Buddhist origin of knowledge and belief is based on Buddha thoughts partly but mostly among Nepalese is based on Indian Brahmin philosophers of Buddhism, Nagarjuna and Guru Padamsambhav's thoughts and ideas that also very much inflicted by Bonism, an ancient Tibetan societal belief system.
Therefore, there is no purity of knowledge as per the law of nature that human can learn from mother nature based on our experience depending upon our curiosity to learn and challenge our thoughts to change according to the law of nature that always move forward for the growth and development through three processes-evolution, revolution and devolution.