Tao or Dao is a Chinese concept signifying 'way', 'path', 'route', or sometimes more loosely, 'doctrine' or 'principle', or as a verb, speak. Within the context of traditional Chinese philosophy and religion, Tao is a metaphysical concept originating with Laozi that gave rise to a religion (Wade-Giles, Tao Chiao; Pinyin, Daojiao) and philosophy (Wade-Giles, Tao chia; Pinyin, Daojia) referred to in English with the single term Taoism. The concept of Tao was later adopted in Confucianism, Chan and Zen Buddhism and more broadly throughout East Asian philosophy and religion in general. Within these contexts Tao signifies the primordial essence or fundamental nature of the universe. In the foundational text of Taoism, the Tao Te Ching, Laozi explains that Tao is not a 'name' for a 'thing' but the underlying natural order of the universe whose ultimate essence is difficult to circumscribe. Tao is thus "eternally nameless" (Dao De Jing-32. Laozi) and to be distinguished from the countless 'named' things which are considered to be its manifestations.
In Taoism, Chinese Buddhism and Confucianism, the object of spiritual practice is to 'become one with the tao' (Tao Te Ching) or to harmonise one's will with Nature (cf. Stoicism) in order to achieve 'effortless action' (Wu wei). This involves meditative and moral practices. Important in this respect is the Taoist concept of De (virtue).
In all its uses, Tao is considered to have ineffable qualities that prevent it from being defined or expressed in words. It can, however, be known or experienced, and its principles (which can be discerned by observing Nature) can be followed or practiced. Much of East Asian philosophical writing focuses on the value of adhering to the principles of Tao and the various consequences of failing to do so. In Confucianism and religious forms of Taoism these are often explicitly moral/ethical arguments about proper behavior, while Buddhism and more philosophical forms of Taoism usually refer to the natural and mercurial outcomes of action (comparable to karma). Tao is intrinsically related to the concepts yin and yang (pinyin: yinyang), where every action creates counter-actions as unavoidable movements within manifestations of the Tao, and proper practice variously involves accepting, conforming to, or working with these natural developments.
The concept of Tao differs from conventional (western) ontology : it is an active and holistic conception of Nature, rather than a static, atomistic one. It is worth comparing to the original Logos of Heraclitus, c. 500 BC