Within the Nyāya tradition, the pursuit of truth is articulated through four principal means of valid knowledge, known as pramāṇas. The first is **pratyakṣa**, or perception, which arises from the direct contact of the senses with their objects. This includes awareness through sight, hearing, touch, taste, and smell, and it is regarded as valid only when it is definite, non-illusory, and free from doubt or error. Perception thus serves as the most immediate disclosure of reality, grounding the other methods in lived experience.

From this basis, Nyāya unfolds **anumāna**, or inference, as a disciplined form of reasoning. Here, knowledge is gained by recognizing an invariable relation (vyāpti) between a sign (hetu) and what it indicates (sādhya). A classic illustration is the judgment that there is fire on a hill because smoke is seen there, coupled with the understood rule that wherever there is smoke, there is fire. This method relies on a structured movement of thought—from a particular case, through a known universal relation, to a new, yet warranted, conclusion.

A third method, **upamāna**, or comparison, reveals how similarity itself can become a bridge to understanding. Knowledge arises when an unfamiliar object is recognized through its resemblance to something already known. For example, after hearing that a certain wild animal (such as a gavaya) is like a cow, one later encounters such a creature and, by noting the similarity, grasps its identity. In this way, analogy clarifies meaning and extends comprehension without abandoning the firm ground of prior experience.

Finally, Nyāya acknowledges **śabda**, or verbal testimony, as a legitimate and necessary source of knowledge. This refers to the words of a trustworthy authority (āpta), whether in sacred scripture or in the statements of competent, honest individuals. Such testimony is counted as valid when it is free from deceit and error, allowing access to truths that may lie beyond the reach of direct perception or personal inference. Together, these four pramāṇas form a coherent discipline of knowing, in which perception, reasoning, comparison, and reliable testimony interlock to guide the seeker toward a more accurate apprehension of reality.