Lecture by Swami Tattwamayananda. Swami Vivekananda says that Samprajnata Samadhi allows mastery over nature, but Asamprajnata Samadhi allows freedom from nature. Buddha had to negate all the hundreds of memories from previous life cycles when he sat for meditation to reach the highest realization. The eighteenth sutra explains that Virama Pratyaya, the negation of impressions, leads us to the highest. The thoughts that come up in meditation can be resolved back into their fundamental cause, the Chitta, mind-stuff. This process of involution is explained. By constant practice, renunciation, Yamas and Niyamas, the mind-stuff is cleaned and we are able to transcend the mind itself. Verses: I.17, I.18