There is not much firsthand information about Leonardo's religious inclination, but most historians have deemed him as a Roman Catholic. Leonardo was not a particularly devout man, but referred to God as a kind of supreme being. Leonardo could be described as a spiritual metaphysician, who was interested in Greek philosophy such as that of Plato and Aristotle. He describes friars as the "fathers of the people who know all secrets by inspiration" and calls books such as the Bible "supreme truth", while also jesting that "Many who hold the faith of the Son only build temples in the name of the Mother."