Within the Vaisheshika vision, atomistic realism and the notion of time are woven together through the problem of change. Reality is said to consist of eternal, indivisible atoms of earth, water, fire, and air, which themselves neither originate nor perish. What begins and ends are the composite bodies formed from these atoms, their unions and separations. Time, understood as kāla, provides the ordered sequence in which these configurations arise, endure for a while, and dissolve. Without such an ordering principle, the succession of states in which aggregates appear, transform, and disappear would lack an intelligible structure.

Time in this system is not a mere abstraction but a real, eternal, all-pervading substance, a dravya distinct from the atoms. It is not composed of atoms and is not reducible to motion or change in them; rather, it is the condition that makes “before and after,” “earlier and later,” and duration itself possible. Although time is imperceptible in itself, it is inferred from the sequential changes in atomic arrangements—succession, simultaneity, priority, and posteriority among events in the world of composites. In this sense, time functions as the subtle background that allows the impermanence of atomic combinations to be experienced and spoken of.

From the standpoint of causality, time furnishes the framework within which causes and effects among atomic aggregates can be distinguished and related. It allows the ordered sequence of production and destruction of composite objects to be understood as a coherent process rather than a mere jumble of occurrences. Time is one universal substance, yet it manifests through particular temporal relations—such as simultaneity, succession, and duration—that govern specific atomic events. Thus, in Vaisheshika thought, the atomistic structure of reality and the reality of time are mutually implicated: atoms provide the enduring constituents, while time grants the ordered flow in which their combinations and transformations become a meaningful cosmos.