This book presents key documents from the pre-1915 history of the extraterrestrial life debate. Introductions and commentaries accompany each source document, some of which are published here for the first time or in a new translation. Authors included are Aristotle, Lucretius, Aquinas, Galileo, Kepler, Pascal, Fontenelle, Huygens, Newton, Pope, Voltaire, Kant, Herschel, Paine, Chalmers, Whewell, Darwin, Wallace, Dostoevsky, Lowell, and Antoniadi, among others. Book jacket.