The burden of the teachings of this sect is subjective idealism. They embrace principles enjoining complete indifference to mundane affairs, and, in fact, thorough personal nullification and the ignoring of all actions by its disciples. In these teachings, thought only, is real. As we have already seen with the Ku-sha teaching, human beings are of three classes, divided according to intellect, into higher, middle and lower, for whom the systems of teachings are necessarily of as many kinds. The order of progress with those who give themselves to the study of the Hossō tenets, is,[12] first, they know only the existence of things, then the emptiness of them, and finally they enter the middle path of "true emptiness and wonderful existence." From the first, such discipline is long and painful, and ultimate victory scarcely comes to the ordinary being. The disciple, by training in thought, by destroying passions and practices, by meditating on the only knowledge, must pass through three kalpas or aeons. Constantly meditating, and destroying the two obstacles of passion and cognizable things, the disciple then obtains four kinds of wisdom and truly attains perfect enlightenment or Pari-Nirvana. The San-ron Shu, as the Three-Shastra sect calls itself, is the sect of the Teachings of Buddha's whole life.[13] Other sects are founded upon single sutras, a fact which makes the student liable to narrowness of opinion. The San-ron gives greater breadth of view and catholicity of opinion. The doctrines of the Greater Vehicle are the principal teachings of Gautama, and these are thoroughly explained in the three shastras used by this sect, which, it is claimed, contain Buddha's own words. The meanings of the titles of the three favorite sutras, are, The Middle Book, The Hundred, and The Book of Twelve Gates. Other books of the canon are also studied and valued by this sect, but all of them are apt to be perused from a particular point of view; i.e., that of Pyrronism or infinite negation. There are two lines of the transmission of this doctrine, both of them through China, though, the introduction to Japan was made from Korea, in 625 A.D. Not to dwell upon the detail of history, the burden of this sect's teaching, is, infinite negation or absolute nihilism. Truth is the inconceivable state, or, in the words of the Japanese writer: "The truth is nothing but the state where thoughts come to an end; the right meditation is to perceive this truth. He who has obtained this meditation is called Buddha. This is this doctrine of the San-ron sect." This sect, by its teachings of the Middle Path, seems to furnish a bridge from the Hinayana or Southern school, to the Mahāyanā or Northern school of Buddhism. Part of its work, as set forth by the Rev. Kō-chō Ogurasu, of the Shin sect, is to defend the authenticity, genuineness and canonicity of the books which form the Northern body of scriptures.