Scientists tend to be ... Utopian in temperament—to believe in the possibility in principle, perhaps even in fact, of a different and altogether better world. The great days of Utopian thinking were the days when voyages of discovery on the earth's surface had the same significance as space travel has today. The old Utopias—New Atlantis, Christianopolis and the City of the Sun—were faraway contemporary societies, but the Utopias men dream of today lie in the distant future or on a planet of a distant faraway sun. Arcadian thinking looks not forward nor far away but backward to a golden age that could yet return. Arcadia is a world of innocence not yet corrupted by ambition and inquiry, a world of pious acquiescence in the established order of things, without strife and without ambition—a world of "truth and honest living." Milton, whom I quote, saw it as the purpose of education "to repair the ruins of our first parents," to return to the happy innocence of the world before the Fall.