How do we know what we know? This subject is called epistemology. Here, we try to understand how knowledge is created. This subject was a part of intellectual discourse in ancient India, under the subject Nyaya. Today, “nyaya” means justice. But in ancient times, it meant rational thinking that enabled us to arrive at facts.

So, people kept asking how we know what we know: what is true and what is false.  There are many, many methods that were identified by ancient Indians on how we know what is fact and what is not. The first method is known as Pratyaksha to actually witness something. When you witness something, you gather data. Facts are gathered through observation. The second is Anumana, based on the data, gained from observations, you infer things. Also, even if you may not actually witness an event, you can infer things. For example, if you can see smoke, you can infer there has been fire. Then comes Upaman, which is based on measurement. Now, measurement plays a very important role in science. We measure and compare things to arrive at a conclusion. And the fourth is Shabda, which is testimony, where you trust the person speaking.