Sima Tan (司馬談) 165-110 BC was a grand historiographer and astrologer of the Western Han dynasty, who classified the philosophy of his time into six main traditions. Of the six, Sima Tan favoured Daoism as the one school among them with the breadth of thought to encompass the others.
The School of Yin and Yang (陰陽家）: Yin and Yang, the well-known concept of a duality of opposed but complementary powers in the universe, was classified as its own school by Sima Tan. It was Yin Yang practitioners who advised the first emperor of China in his quest for immortality. Sima Tan rates their idea of keeping in harmony with the four seasons (四時之大順，不可失也) but says they are superstitious and keep people bound in fear. The yin-yang cosmology was already being incorporated into other philosophical schools by this time.
The School of Yin Yang
The School of Ru (儒家): Better known in the Western world as Confucianism, the lineage of thinkers such as Confucius and Mencius is given short shrift by Sima Tan. He approves of their finely graded approach to ceremony, but is snobby about their efforts to achieve moral rectitude by force of will, an attempt he sees as ultimately futile. This philosophical tradition which would come to dominate Chinese society is quickly dismissed as 'learned but short on the essentials' (博而寡要，勞而少功).
The School of Ru
The Mohist School (墨家): Practical, frugal and utilitarian, the Mohist school was named after its founder Mo Di, probably a low-status artisan. The Mohist texts are written in a stodgy and unrefined style, focused on the useful and economical; the school held little truck with the lofty pretensions of other philosophies, though there is a strong morality to Mohist thought. Sima Tan approves of the Mohists' frugality up to a point, but thinks they take the principle too far.
The Mohist School
The School of Law (Legalists): In the tumultuous 3rd century, a group of thinkers emerged who focused on statecraft and realpolitik, jettisoning the niceties of morality. Well-known texts from this school include the Han Fei Zi and The Book of Lord Shang. In Sima Tan's view, some of the group's strategies might be useful in the short term, but the harshness and lack of charity (嚴而少恩) make it a poor choice for the long haul. Despite this, Sima Tan approves of the strong differentiation between ruler and subject.
The School of Law
The School of Names (名家): Is a white horse a horse? Perhaps not, depending on your point of view. The School of Names is the name Sima Tan gives to a group of thinkers who delighted in wrangling with the niceties of language and categories to challenge and dispute apparent truisms. There are parallels with the sophists of Ancient Greece, in the hair-splitting approach to argumentation. Sima Tan sees this as glib obfuscation of the truth, but useful for sharpening thinking.
The School of Names
The School of the Way and its Potency (道德家）: This is the name Sima Tan gives to the school of thought typified by Laozi, Zhuangzi and the Huang-Lao school. One key idea is wu wei (無為): achieving all things by staying in harmony with the ebb and flow of the universe. According to Sima Tan, the School of the Way and its Potency is the smart choice for those in the market for philosophy: it takes the best of the other five schools and knows how to move with the times.
The School of the Way