The Ājīvika school is known for its Niyati (Fate) doctrine of absolute fatalism or determinism,[6][8][15] the premise that there is no free will, that everything that has happened, is happening and will happen is entirely preordained and a function of cosmic principles.[6][8][12] The predetermined fate of living beings and the impossibility to achieve liberation (moksha) from the eternal cycle of birth, death, and rebirth was the major distinctive philosophical and metaphysical doctrine of their school of Indian philosophy. Ājīvikas further considered the karma doctrine as a fallacy.[16] Ājīvika metaphysics included a theory of atoms which was later adapted in the Vaiśeṣika school, where everything was composed of atoms, qualities emerged from aggregates of atoms, but the aggregation and nature of these atoms was predetermined by cosmic laws and forces. Ājīvikas were mostly considered as atheists.[18] They believed that in every living being is an ātman – a central premise of Vedic religion and Jainism.

Ājīvika means Follower of the Way of Life

Atomism Ajivikas developed a theory of elements and atoms similar to the Vaisheshika school of Vedic's. Everything was composed of minuscule atoms, according to Ajivikas, and qualities of things are derived from aggregates of atoms, but the aggregation and nature of these atoms was predetermined by cosmic forces.[17]

The description of Ajivikas' atomism is inconsistent between those described in Buddhist and Vedic texts. According to three Tamil texts,[58] the Ajivikas held there exists seven kayas (Sanskrit: काय, assemblage, collection, elemental categories): pruthvi-kaya (earth), apo-kaya (water), tejo-kaya (fire), vayo-kaya (air), sukha (joy), dukkha (sorrow) and jiva (life). The first four relate to matter, the last three non-matter. These elements are akata (that which is neither created nor destroyed), vanjha (barren, that which never multiplies or reproduces) and have an existence independent of the other.[17] The elements, asserts Ajivika theory in the Tamil text Manimekalai, are made of paramanu (atoms), where atoms were defined as that which cannot be further subdivided, that which cannot penetrate another atom, that which is neither created nor destroyed, that which retains its identity by never growing nor expanding nor splitting nor changing, yet that which moves, assembles and combines to form the perceived.

The Tamil text of Ajivikas asserts that this coming together of atoms can take diversity of forms, such as the dense form of a diamond, or a loose form of a hollow bamboo. Everything one perceives, states the atomism theory of Ajivikas, was mere juxtapositions of atoms of various types, and the combinations occur always in fixed ratios governed by certain cosmic rules, forming skandha (molecules, building blocks). Atoms, asserted the Ajivikas, cannot be seen by themselves in their pure state, but only when they aggregate and form bhutas (objects). They further argued that properties and tendencies are characteristics of the objects. The Ajivikas then proceeded to justify their belief in determinism and no free will by stating that everything experienced – sukha (joy), dukkha (sorrow) and jiva (life) – is mere function of atoms operating under cosmic rules.

Riepe states that the details of the Ajivikas theory of atomism provided the foundations of later modified atomism theories found in Jain, Buddhist and Vedic traditions

• Nature (the universe or cosmos) consists only of natural elements, that is, of spatio-temporal physical substance – mass –energy. Non-physical or quasi-physical substance, such as information, ideas, values, logic, mathematics, intellect, and other emergent phenomena, either supervene upon the physical or can be reduced to a physical account;