What is knowledge? What are the sources of knowledge? What are things that we can know about a subject? What are things that we can never be sure about? These are questions that have arisen in the minds of many philosophers from the earliest days. A systematic study of knowledge - what is knowledge, how we gather knowledge, and the scope of the subject at hand - is called "epistemology" [eh-piss-stem-all-uh-jee]. It is one of the branches of philosophy.
The earliest epistemological ideas come from ancient India. Further, epistemology as a system also seems to have come from India with the advent of the Nyaya School of philosophy, which originated between 500 and 200 BCE. Akshapada Gautama wrote an influential text called the Nyaya Sutras, which shaped the Nyaya School as we have known it for the past 2,000 years. That apart, every other school of Indian philosophy also has its views about epistemology.
Now let us take a look at the three elements involved in acquiring knowledge:
jñātr - is the person who seeks knowledge; "the knower"
jñeya - is that which can be known; "the knowable"
jñāna - is that which is known; "knowledge"
The relationships between these three elements vary according to the school of philosophy and in turn influence their epistemology.
For example, according to the Nyaya School, these three elements are eternally separate while according to the Advaita Vedanta School, these three elements are actually one.
One of the fundamental concepts put forth by Indian philosophers is that of pramāna - the methods and means by which knowledge is obtained. Depending on the school of philosophy, different pramānas are accepted.
The basic pramāna that is acceptable to all schools of philosophy is pratyaksa, "direct perception". This refers to knowledge that is acquired through our sense perceptions and in addition has the following three qualities:
1. We should sure about what we perceive; for example, if I look into the distance, I cannot be sure if what I'm seeing is smoke or dust
2. What we are perceiving may not be related to its name; for example, irrespective of what it's called in different languages, fire remains what it is
3. We know that what we perceive is not a sensory illusion, like a mirage or an echo
The Lokayata school (Charvakism) considers only this pramāna and no other.
The Bauddha (Buddhism) and Vaisheshika schools accept a second pramāna, which is anumāna, "inference". This refers to knowledge that comes before direct perception. It is an inference based on certain observations. There are three kinds of inferences:
1. Inferring about the future; for example, when we see clouds we infer that it will rain
2. Inferring about the past; for example, when we see wet streets we infer that it has already rained
3. Commonly observed; for example, when we see smoke we infer that there has been a fire
A few of the Bauddha Schools also accept the words of the Buddha and other saints as a legitimate source for knowledge but in general, they accept only two pramānas - direct perception and inference.
The Jaina (Jainism), Samkhya, Yoga, Vishishtadvaita Vedanta and Dvaita Vedanta Schools accept a third pramāna, which is śabda (or āgama), "verbal testimony" (or "authority of the scriptures"). This refers to a meaningful statement uttered by a reliable person. This reliable person could be anyone whom we trust - an old woman at the street corner or the seers of the Vedas.
Verbal testimony is of two kinds:
1. One that can be seen and thus easily verified; for example, when we have lost our way, we ask people for directions
2. One that cannot be seen and thus not easily verified; for example, when we ask our spiritual guru for guidance, she tells us to meditate everyday to attain salvation
The Nyaya School accepts a fourth pramāna, which is upamāna, "comparison". This refers to acquiring knowledge about something by comparing it with what we already know. For example, if I want to explain cricket to someone in the US, I can use their existing knowledge of baseball.
The Prabhakara Mimamsa School accepts a fifth pramāna, which is arthāpatti, "presumption". This refers to postulation based on certain observations and using common sense. For example, if I find that my roommate's shoes are missing, I postulate that he has gone out - assuming of course that he's alive and that he needs his shoes when he goes out. The Nyaya School puts presumption under the category of inference.
The Bhatta Mimamsa and Advaita Vedanta Schools accept a sixth pramāna, which is anupalabdhi, "non-perception". It refers to something that cannot be perceived. For example, "This article does not have any Russian words" is a form of knowledge. Further, this lack of perception may be of four types:
1. We cannot perceive the cause
2. We cannot perceive the effect
3. We cannot perceive the object
4. We cannot perceive the contradiction
This pramāna is particularly useful when the other five fail.
Finally, those who believe in the Puranas - the Pauranikas - accept two other pramānas - sambhava, "probability" and aitihya, "legend, rumour".
In today's world of information overload, we acquire knowledge from so many sources. But how valid are these sources? To what extent can you rely upon a newspaper article or even a television programme? It is important to be aware about our sources of knowledge - are they eyewitness accounts, are they from the primary texts of a particular subject, can the knowledge be verified, does a piece of writing contradict something established, does a lecturer contradict himself, and so on.
In fact, it is because of this methodical approach to knowledge that nyaya possibly became the earliest system of thought that could produce both atheists and theists, each side providing beautiful and compelling arguments in their defence.