Maya (Sanskrit) [from the verbal root ma to measure, form] Illusion, the non-eternal; in Brahmanical philosophy, the fabrication by the human mind of ideas derived from interior and exterior impressions, as it tries to interpret and understand the universe. While the exterior world exists -- or it could not be illusory -- we do not see clearly and as they actually are that which our mind and senses present to us. A traditional Vedantic illustration says that at twilight a person sees a coiled rope on the ground and springs aside, thinking it is a snake; the rope is there, but no snake.
Thus maya means that our minds are blinded and perverted by our own preconceptions and imperfections, and so does not interpret the world as it is.
"Maya or illusion is an element which enters into all finite things, for everything that exists has only a relative, not an absolute, reality, since the appearance which the hidden noumenon assumes for any observer depends upon his power of cognition. . . . Nothing is permanent except the one hidden absolute existence which contains in itself the noumena of all realities. The existences belonging to every plane of being, up to the highest Dhyan-Chohans, are, in degree, of the nature of shadows cast by a magic lantern on a colourless screen; but all things are relatively real, for the cogniser is also a reflection, and the things cognised are therefore as real to him as himself. Whatever reality things possess must be looked for in them before or after they have passed like a flash through the material world; but we cannot cognise any such existence directly, so long as we have sense-instruments which bring only material existence into the field of our consciousness.
Whatever plane our consciousness may be acting in, both we and the things belonging to that plane are, for the time being, our only realities. As we rise in the scale of development we perceive that during the stages through which we have passed we mistook shadows for realities, and the upward progress of the Ego is a series of progressive awakenings, each advance bringing with it the idea that now, at last, we have reached 'reality'; but only when we shall have reached the absolute Consciousness, and blended our own with it, shall we be free from the delusions produced by Maya" (SD 1:39-40).
Though sometimes used as an equivalent for avidya, maya is properly applicable only to prakriti, which is doomed to disappear at the time of pralaya. It is thus prakriti and its productions or changes (vikaras) which, by reacting against the operations of the consciousness of a perceiving being, casts the perceiver into the bonds of illusions, out of which the deluded being has to strive in order to free himself from the maya with which he is surrounded.
"Just as milliards of bright sparks dance on the waters of an ocean above which one and the same moon is shining, so our evanescent personalities -- the illusive envelopes of the immortal monad-ego -- twinkle and dance on the waves of Maya. They last and appear, as the thousands of sparks produced by the moon-beams, only so long as the Queen of the Night radiates her lustre on the running waters of life: the period of a Manvantara; and then they disappear, the beams -- symbols of our eternal Spiritual Egos -- alone surviving, re-merged in, and being, as they were before, one with the Mother-Source" (SD 1:237).