Nyaya is to test subjects by evidence. The cause of Prama is called Pramaan. Prama means real experience. Business specific extraordinary reason is called Karan. In this way, the business specific extraordinary cause of real experience is called Pramana. There are four types of real experience – direct, permitted, upatimit, and from the difference of words. Evidence is also of four types – direct, inference, comparison and difference of words. There are two types of philosophy – with the difference between a theist and an atheist. The philosophy which accepts the authority of the Vedas is called theistic philosophy. The philosophy which does not accept the evidence of Vedas is called atheistic philosophy. Theistic philosophies are of six types – Nyaya, Vaiseshik, Samkhya, Yoga, Mimansa and Vedanta. There are three types of atheistic philosophy – from the distinction of Charvak, Jain and Buddhist. There are four types of Buddhist philosophy – with the distinction of Vaibhashik, Sautrantik Madhyamik and Yogachar. Thus there are 12 types of philosophy. Nyaya is also a philosophy in these philosophies. In this, subjects are tested through evidence. Ghatpatadi is made visible through direct evidence. Presumption is allowed by evidence. Sub-measure is done by sub-paramana. Word understanding is done through word evidence. In this way, testing the subjects by the four proofs is called Nyaya.