Sri Aurobindo (Bengali: শ্রী অরবিন্দ Sri Ôrobindo) was an Indian nationalist and freedom fighter, major Indian English poet, philosopher, and yogi. He joined the movement for India's freedom from British rule and for a duration (1905–10), became one of its most important leaders, before turning to developing his own vision and philosophy of human progress and spiritual evolution. The central theme of Sri Aurobindo's vision is the evolution of life into a "life divine". In his own words: "Man is a transitional being. He is not final. The step from man to superman is the next approaching achievement in the earth evolution. It is inevitable because it is at once the intention of the inner spirit and the logic of Nature's process." The principal writings of Sri Aurobindo include, in prose, The Life Divine, considered his single great work of metaphysics,The Synthesis of Yoga, Secrets of the Vedas, Essays on the Gita, The Human Cycle, The Ideal of Human Unity, Renaissance in India and other essays, Supramental Manifestation upon Earth, The Future Poetry, Thoughts and Aphorisms and several volumes of letters. In poetry, his principal work is Savitri: a Legend and a Symbol in blank verse.