The first momentous discovery with metaphysical implications of the first order towards which science arduously laboured its way was that matter is in the end only an illusory appearance. The next great discovery of a similar character has already begun and it will finish with the corollary that time and space are also in the end illusory appearances. But as the world in which we live and the only one which we ordinarily know is a material, temporal, and spatial one, it follows that mankind is beset by the profoundest illusions. Thoroughly to understand the significance of illusions, however, is to understand that in the end it is the working of the Mind alone that plays these tricks on man and clothes the world for him in matter, time, and space. If therefore he wishes to free himself from these three universal illusions he must achieve conscious control of the mind's activity. This he can succeed in doing through Yoga; concentration on a single thought theme or object, when persisted in to the bitter end, stops such mental activity and thus the illusions which accompany it also stop.
-- Notebooks Category 19: The Reign of Relativity > Chapter 1 : The Cosmos of Change > # 65
