Astik, derived from Asti, which means "there is", refers to a school of thought that accepts the authority of the leading belief pattern established during that period.

The concept of atheism is fluid among the Indian philosophies. Depending on their period of reference, this belief evolved.

For example, during the Vedic ages (1500-1100 BC), the belief in the spiritual texts, the Vedas, reference Astik as believers or Nastiik as non-believers. Similarly, those who believe in Karma or in the existence of God are referred to as Astik and those who don't Nastik.

Across the world, atheism has gathered a negative vibe in spirituality, while in the Indian subcontinent there has been a long standing tradition of atheism. Few of the religions that are solely based on atheism are Buddhism, Jainism and Charvak. The Indian Philosophy states that every person is entitled to choose their own belief/s, are encouraged to question and to establish their own meaning to spirituality.