Knowledge of the truth of the Self is obtained only by Self-enquiry, and not by any number of actions. One who mistakes a rope for a serpent is cast into fear, thereby and his fear and distress can be removed only by the knowledge that it is a rope.
A friend who knows this, tells him so and he investigates and finds that it is so. There is no other way.
-- Vivekachudamani (from Collected Works of Sri Ramana Maharshi)