How Do We Know What We Know?

We each hold thousands of beliefs: that the earth orbits the sun, that a friend is trustworthy, that a medicine is safe, that we are not good at mathematics. Few of these have been examined. Epistemology — the study of knowledge — asks what justifies a belief and how we can tell knowledge from mere opinion.

Indian philosophy developed one of the world's richest traditions on this question, centred on the idea of pramāṇa: a valid means or source of knowledge.

Different darśanas (schools of philosophy) accepted different lists of pramāṇas. A simplified overview:

• Pratyakṣa (perception): direct knowledge through the senses. Accepted by virtually all schools, including the Cārvāka materialists, who accepted only perception.
• Anumāna (inference): reasoning from what is perceived to what is not — the classic example being inferring fire from smoke. Accepted by most schools, including Buddhist logicians.
• Śabda (testimony): knowledge from reliable words, whether of a trustworthy person or, for some schools, of scripture. Nyāya accepted it; Buddhist epistemologists such as Dignāga and Dharmakīrti did not treat it as a separate source.
• Upamāna (comparison): learning what something is through similarity to something known. Accepted by Nyāya and Mīmāṃsā.
• Arthāpatti (postulation) and anupalabdhi (non-perception): accepted by some Mīmāṃsā and Vedānta thinkers.

These categories map surprisingly well onto modern questions. Much of what we "know" comes from testimony — teachers, books, news, social media — which makes the reliability of sources a central issue today. Inference can be strong or weak, and Indian logicians developed careful tests for when an inference is valid, including attention to counter-examples.

Asking "which pramāṇa supports this belief?" is a quick way to see whether a belief rests on direct experience, reasoning, someone else's word or simply habit.

Western epistemology has long debated similar questions: empiricists emphasised experience, rationalists emphasised reason, and later philosophers examined testimony and the social dimension of knowledge. Modern science adds systematic methods — controlled observation, replication, peer review — for reducing error.

Contemplative traditions add a further claim: that some forms of knowing, such as direct insight into one's own mind, are developed through practice rather than argument. Whether such insight counts as knowledge, and how it could be checked, is itself an important philosophical question.

The aim is not to doubt everything, which is impossible, but to hold beliefs with confidence proportional to their support — and to remain open to correction.