This discussion paves the way for an outline of epistemological methods in which the rationalism of thinkers like Descartes, Leibniz and Kant is compared to the empiricism of Locke and Hume.Over the course of the book, in a manner that is careful and methodic but never dull, Jeans marshals the evidence for his startling conclusion: recent discoveries in astronomy, mathematics, sub-atomic physics and other disciplines have washed away the scientific basis of many older philosophic discussions. Such long-standing problems as causality, free will and determinism, the nature of space and time, materialism and mentalism must be considered anew int he light of new knowledge and information attained by 20th-century physical science. Even then, however, Jeans cautions against drawing any positive conclusions, pointing out that both physics and philosophy are both relatively young and that we are still, in Newton's words, like children playing with pebbles on the sea-shore, while the great ocean of truth rolls, unexplored, beyond our reach.Although first published nearly 40 years ago, nothing in physics has happened to affect Jean's account in this book; it remains remarkably fresh and undated, a classic exposition of the philosophical implications of scientific knowledge.