Vaisheshika’s atomistic realism rests primarily on careful reasoning about divisibility, size, and change. Observing that any composite object can be divided into smaller and smaller parts, its thinkers argue that this process cannot proceed without limit; otherwise, no concrete, determinate thing would ever truly exist, and finite objects would paradoxically contain an infinite number of parts. To avoid such an infinite regress, they posit indivisible units—paramāṇus or atoms—as the ultimate building blocks of matter. The existence of finite, measurable bodies is thus taken as evidence that there must be smallest, partless constituents that ground the determinate size of things.

This line of thought is closely tied to their reflections on production and destruction. Composite substances are seen to arise through the combination of parts and to perish through their separation, yet some enduring substrate is required to make sense of this continuity through change. Atoms serve as these eternal, unchanging entities whose various combinations and separations give rise to the birth, transformation, and dissolution of observable objects. The breaking of a pot, for example, is interpreted not as annihilation of substance, but as the disaggregation of an atomic compound, preserving a continuity of causal powers beneath the flux.

Vaisheshika also infers atoms from the structure and diversity of the world that is directly perceived. Even the smallest visible units—like specks of dust or tiny drops—are treated as compounds, suggesting that what appears as “smallest” to the senses is still composed of more fundamental, imperceptible elements. From this they reason to dyads, triads, and larger groupings of atoms, which alone can account for the observable gradations of quantity and the emergence of new qualities in aggregates. The regular, lawlike differences among substances—earth, water, fire, and air—are further taken to imply distinct atomic types, each bearing characteristic potential qualities that manifest at the macroscopic level.

Underlying these arguments is Vaisheshika’s broader ontological scheme of categories (padārthas), within which atoms occupy a privileged place. As ultimate substances (dravya), they are the bearers of qualities (guṇa) and motions (karman), and they stand in inherence relations (samavāya) that bind them into larger wholes. Each atom is marked by a particularity (viśeṣa) that prevents total indistinguishability, allowing a world of many concrete entities rather than a featureless mass. Within this systematic framework, the postulation of eternal, indivisible, qualitatively distinct atoms is presented not as an arbitrary hypothesis, but as the most coherent way to make sense of finite size, causal continuity, and the ordered diversity of the physical world.