Apaurusheya (Infallibility) is a term related to the authenticity of the words or books written. Many people familiar to us might have written books. They might be excellent and unbeatable scholars in a multitude of subjects. By that way, such people will be enjoying the attention and pampering of the mainstream society. But those who are in a spiritual realm will consider those works a bit inferior. The reason is that the authors of these works are not having any divine powers (siddhis).
Human beings are considered to be imperfect in many sectors. Considering the physical as well as mental abilities, along with the technical expertise to overcome these imperfections, notable development is there in many spheres, but perfection is still an illusion in the case of human race. These physical and mental imperfections will certainly reflect in their day to day life. Similar is the case with writing books. It is said that all the books ever written by the humans, no matter what, have got imperfections in one or the other way.
If these are the facts, will there be any perfect book? If yes, who will be the author of that book? The answer is very simple. Only a book written by Isvara can be deemed as perfect. As God is perfect, His works are also perfect. Hence, the term Apaurusheya is coined to denote the unquestionable authenticity of the creations authored by God, either directly or indirectly.
Those books which are considered to be Apaurusheya are written by humans only, but the contents of such books will be decided by Isvara. In order to understand the matters decided by the Isvara, man has to keep aside his humane nature and attain a stage of Nirvana or Moksha (liberation). As far as man continues to be in his common state of being, he cannot understand the divine decisions. A yogi who is indulged in a state of Nirvana can understand the wish of the God. That eventually reaches the hands of human beings in the form of a book. According to Bharatiya darshana, the authenticity of such works as absolutely unquestionable.
There are some remarkable works in Indian philosophy which are considered to be Apaurusheya. Vedas, Brahmanas, Aranyakas, Upanishads, words of wisdom from Buddha and the preaching of Thirthankaras belong to this stream.
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