[raison d'etre = reason or justification for existence]
Insight, i.e. the ability to see one's own self, means freedom from the emotional experience of joy and sorrow. Until and unless one frees oneself from this tinted outlook, one cannot realise the truth. One may become very learned, an erudite scholar, or may acquire proficiency in theoretical philosophy, but one cannot obtain insight.
Truth is synonymous with insight, right faith and right attitude etc. Meditational practice aims at developing insight so that one can be aware of one's spiritual self, who is the real knower and real seer. A man of science cannot know him, only a sadhaka can do so. By systematic and regular practice of meditation, he (the practitioner) will progressively free his perceptions from the pollution of like and dislike, pleasure and pain. He abandons his role as a 'doer' and assumes the role of 'knower'.