Genuine self knowledge can only be attained by meditation, introspection and objective observation.
Otherwise, one would only be parroting that those who have been previously said and / or realized.
One must also question that which he or she has been told / taught, as well as that which one thinks that he or she understands.
This is one the most basic teachings of Buddhism and one of its distinguishing characteristics. The Buddha told his followers to even question everything he said and to personally accept nothing until one had found the same to be true for themselves.