Pratyakṣa (perception) occupies the foremost position in the Nyāya epistemology. Perception can be of two types, laukika (ordinary) and alaukika (extraordinary). Ordinary perception is defined by Akṣapāda Gautama in his Nyāya Sutra (I, i.4) as a non-erroneous cognition which is produced by the intercourse of sense-organs with the objects.
Indian texts identify four requirements for correct perception: Indriyarthasannikarsa (direct experience by ones sensory organ(s) with the object, whatever is being studied), Avyapadesya (non-verbal; correct perception is not through hearsay, according to ancient Indian scholars, where ones sensory organ relies on accepting or rejecting someone elses perception), Avyabhicara (does not wander; correct perception does not change, nor is it the result of deception because ones sensory organ or means of observation is drifting, defective, suspect) and Vyavasayatmaka (definite; correct perception excludes judgments of doubt, either because of one's failure to observe all the details, or because one is mixing inference with observation and observing what one wants to observe, or not observing what one does not want to observe).
Ordinary perception to Nyāya scholars was based on direct experience of reality by eyes, ears, nose, touch and taste. Extraordinary perception included yogaja or pratibha (intuition), samanyalaksanapratyaksa (a form of induction from perceived specifics to a universal), and jnanalaksanapratyaksa (a form of perception of prior processes and previous states of a topic of study by observing its current state).