How Brahman, ‘the One without a second,’ the only Reality, appears as this phenomenal universe, is a question that has baffled the Indian philosophers who have accepted the final authority of the śruti or the Vedas, for ages. Śaṅkara (A. D. 788-820) posits avidyā, ajñāna or māyā as the factor responsible for this. (See AJÑĀNA for details.) Later Advaitins have tried to present māyā as the cause and avidyā or ajñāna as its effect. The latter words have been variously rendered as ‘nescience,’ ‘ignorance,’ ‘non-knowledge’ or even ‘anti-knowledge.’ In the final analysis it defies all definition.

The word ‘avidyā’ has been used by Patañjali (200 B. C.) in his Yogasūtras (2.3-5). He considers it as one of the five ‘kleśas’ or afflictions, but as the ground for the origin of the others. He defines it as that which makes us feel that the transient is eternal, the impure is pure, misery is happiness and the non-self is the Self. It can be eliminated only by ‘viveka-khyāti’ the knowledge that we as the Self (which is pure consciousness) are entirely separate and different from prakṛti or insentient nature.