Darkness can be ended only with the help of light. Darkness cannot be overwhelmed by attacking it with more darkness. Spiritual knowledge (vidya) is the light that one needs to destroy the inner darkness. Spiritual learning provides the inner illumination. Spiritual wisdom is the authentic yoga of the Supreme Person (Purusho- thama Yoga) defined in the Gita; it is the knowledge of the Supreme, the higher learning (vidya). This yoga cannot be bought for money or acquired from friends or ordered from concerns or companies. It has to be assimilated and won by each one for oneself, through steady faith and ardent devotion.
Sri Sathya Sai Baba, Vidya Vahini, Chapter2