In our journey as humans, we have always been fascinated by our capacity for knowledge and our self-awareness. No other species has these abilities developed to the level achieved by human beings. Several theories emerging from different parts of the world at different times, have been dedicated to examining and explaining how it is that we get to know about the world around us, through the course of childhood development and maturity. Some of the documented processes of gaining knowledge include Language, Sense perception, Emotion, Reason, Imagination, Faith, Intuition and Memory.
These are not mutually exclusive categories since we can find overlaps and combinations of these, between language and memory, reason and language and so on. In pursuit of the study of epistemology (how we gain knowledge), the Upanishads provide us with multiple, detailed and powerful sources for understanding human mental functioning. It is quite unfortunate that our courses on child development and psychology barely mention theories available in our ancient scriptures, relying heavily on Western philosophical and scientific traditions. I do believe that the association of Hindu philosophy as a religious pursuit has been largely responsible for its separation from institutions of higher learning, and a tremendous loss to the scientific community.
My understanding of our ancient texts is a drop in a vast ocean, and it is only recently that I have started my search. Here is a small taste of what we can find about ways of knowing:
There are believed to be six principal means of knowing, of Pramana. According to Hinduism, Pramana is a theory of knowledge consisting of one or more reliable and valid means by which human beings gain accurate, true knowledge. Hinduism, Buddhism and Jainism have robust debates about what accurate knowledge is, how it is acquired, how one knows and also why one doesn’t. Although some sources identify ten processes and some eight, these six are the most studied ways of knowing (See Bhawuk, 2011 for more details). These are:
Sensation – Pratyaksh
Presumption (using prior knowledge) – Anuman
Analogy (comparisons) – Upaman
Awareness of ABSENCE – Anuplabdhi
Superimposition (of things already known ONTO something new by contradiction – Arthapatti
Words or texts – Shabd
The most fascinating of these is Anuplabdhi or the awareness of absence, and there is some debate between the Nyaya and Vedanta schools of thought about whether Anuplabdhi (or the absence of something) and Arthapatti (contradiction) are valid sources of its knowledge, Vedanata arguing in favour. The discourse in Hindu theories of epistemology is characterized by intense and continuous debate rather than dogma.
 Bhawuk, D. (2011). Spirituality and Indian Psychology. New York: Springer.