The aim of this book is to explain human rationality. The fundamental principles of human thought are stated in terms of Balzer's Principles, and their operations in everyday life are illustrated. The natural numbers are defined and explained in a fresh fashion. Paradoxes, including those of class theory and material implication, which have signaled that all is not well in our logical systems, are laid to rest here. The explanation of human rationality has more than logical interest, for it touches upon the human values embedded in our rationality. The book carries the message that all human beings are fundamentally equal.