Longchen Rabjampa (1308–1364) was a major teacher and writer of the Nyingma school of Tibetan Buddhism. He is widely considered the single most important writer on the Dzogchen teachings.
"We should not mistake the Truth with opinions. Many think that the Truth is this or that, or that the Truth is within this or that book, or within this or that belief or idea, etc. Whosoever wants to experience the Truth should not mistake beliefs, ideas, opinions and theories with that which is the Truth. We must experience the Truth in a direct, practical and real manner; this is only possible in the stillness and silence of the mind, and this is achieved by means of meditation."