This book contains two lectures - given in 1988 and 1989 respectively - which belong to Karl Popper's late work, most of which is still unpublished. The first introduces a new view of causality, based on Popper's interpretation of quantum theory, yet freed of difficulty. It is a new view of the universe - a view that easily merges with the commonsense view that our will is free. The second lecture gives a glimpse of human knowledge as it evolves from animal knowledge. Both lectures have been expanded by Popper for publication.