Are there foundational principles that apply to all human knowledge and are accessible to all? Are entities and causes that lie outside the material realm mere myth? How can we remedy the fragmentation of knowledge and the ensuing schism between a perceived scientific elite and non-scientists? Do we have a framework to remedy this situation? This book updates the foundational principles of science laid down by Aristotle in his metaphysics to provide a rational framework and a "common language" for those inside and outside of the modern scientific enterprise. The book demonstrates how Aristotelian metaphysics approaches knowledge in a methodical, unifying, and yet open manner, seeking answers to the question why? and not just to the question how?, and accepting rational answers even if they lie outside the box of material entities and causes. This timely book is both an accessible primer to the foundations of human knowledge and an exhortation for a unified approach to knowledge.