Astika and nastika

The terms

Astika derives from asti, "it is"; nastika from na asti, "it is not". In the classical doxographies the division is usually made on one question: whether a school accepts the authority of the Vedas.

On that criterion the six astika darshanas are Nyaya, Vaisheshika, Samkhya, Yoga, Mimamsa and Vedanta; the nastika schools are Buddhism, Jainism and Charvaka.

The instability

The criterion is not the only one used. In some texts astika means belief in an afterlife or in the efficacy of action, and in others belief in a god. These do not sort the schools the same way. Samkhya in its classical form does not posit a creator god yet is counted astika because it accepts Vedic authority. Mimamsa, the school most devoted to Vedic ritual, is also not theistic in the usual sense.

Conversely a Buddhist accepts rebirth and moral causation but is nastika because the Vedas are rejected. The categories therefore track a question of authority rather than of belief, and using them as though they meant "believer" and "atheist" produces confusion.

Who applied them

The classification is a product of the astika side. It appears in Brahmanical doxographies that arrange the schools for the purpose of refuting some and ranking others, and it is not how the Buddhists or Jains described themselves.

Jain writers, notably Haribhadra, produced their own surveys of the schools with a different and more even-handed arrangement, consistent with the doctrine of many-sidedness. Modern usage has largely inherited the Brahmanical scheme, which is worth keeping in mind when the six-plus-three arrangement is presented as a neutral map of Indian philosophy.