Nyāya approaches causation with a rigor that is both logical and deeply realist. A cause is understood as that invariable, unconditional, and necessary antecedent whose presence is required for a specific effect to arise. Wherever a particular effect appears, its appropriate causes must have been present; where those causes are absent, the effect cannot occur. This is expressed through the notion of invariable concomitance (vyāpti), which is more than mere regular succession and is grounded in the real nature of things. Cause and effect are also temporally ordered: the cause must precede the effect and cease to be operative once the effect has been produced, even though the underlying material may persist in a transformed state.

Within this framework, Nyāya offers a threefold analysis of causation. The **samavāyī-kāraṇa**, or inherent/material cause, is the substrate in which the effect inheres, such as threads in relation to a cloth or clay in relation to a pot. The **asamavāyī-kāraṇa**, or non-inherent cause, consists of qualities or conditions connected through inherence to the material cause, such as the color or arrangement of the threads that determine the color and structure of the cloth. The **nimitta-kāraṇa**, or efficient cause, is the operative factor—agents and instruments like the weaver and loom or the potter and wheel—that initiate and guide the process of production. For an effect to manifest, all these causal factors must converge in the appropriate manner.

Nyāya also insists on a clear ontological distinction between cause and effect. The effect is a new product, numerically distinct from its causes, and does not pre-exist in them in the same form. This stance, expressed as asatkāryavāda, rejects the idea that the effect is merely a hidden or modified state of the cause; instead, the effect emerges as a novel entity when the relevant causes come together under the right conditions. Yet this emergence is not arbitrary or subjective: it unfolds within an objective, mind-independent causal order that can be known through careful observation and inference. In this way, Nyāya’s reflection on causation becomes both a metaphysical account of how things come to be and a methodological guide for attaining reliable knowledge of reality.