The eighteenth yogic sutra explains about the self-realisation in a sadhaka, when he is capable of perceiving the past lives and its actions. He acquires this through direct perception of imperceptible impressions. Every instinct, wish or desire essays a key role in a person`s life. And when a sadhaka is perfectly liberated from all wants, pains or pleasures, he is able to see clearly his present, past deeds and also the coming time period.

Samskara subliminal impressions, instinct, realization of past perception
saksatkaranat to see in reality, by direct observation, by direct perception, by bringing to the surface of consciousness
purva earlier, previous
jati descent, status in life, lineage, condition, rank, birth
jnanam knowledge

Through direct perception of his subliminal impressions, the yogi gains knowledge of his previous lives.

The yogi is able to recall the impressions of past incarnations which have influenced his present life. In the continuity of life, instinct, memory and desire play significant roles. Memory belongs to the subconscious mind, and the fruits of cravings (pains and pleasures experienced in the present life as a result of good and bad actions in past lives) to the unconscious.

When a yogi is free from every instinct and desire, he sees directly, independent of memory, and of feelings of joy or sorrow. Through intuition, in the orderly sequence of time, he actually sees his past lineage and future status, and also the lives of others. (II.12, 13, 39, and iv.33.)