AI is dazzling, but the human mind remains unmatched. This work serves as an urgent call to action for human minds. AI's entry into the domain of intelligence elicits both enthusiasm and fear. It also provides an epochal opportunity to focus on the most exquisite phenomenon known to us: the human mind. The human reasoning mind possesses what we call "common sense." This humble term conceals the unfathomable depths of human reason. Our science recognizes that human babies are born with consciousness and reflective thinking capabilities. However, we know very little about the origins and inner workings of these foundations of human reason. Building on them, human minds can acquire knowledge and common sense. This book explores what we know, what we pretend to know (our beliefs masquerading as scientific facts), and what humanity indeed knew at the dawn of Western civilization when human reason was elevated to a position where it became an increasingly trustworthy and reliable instrument. How did it all start, and how were we able to leave irrational beliefs and damaging traditions behind? We know that the pioneers of philosophy knew how to curb the irrational aspects of human reason, limit the influence of raw self-interest, and usher in an era of humanism.Modern humanity, dazzled by new shiny technological toys, has all but forgotten such age-old faculties, even though they are preserved in the Perennial Philosophy. Effective global cooperation is needed to meet upcoming challenges, but it is becoming obvious that, on the whole, humans are way too selfish, glaringly unwilling to cooperate on a global scale, and unprepared for global challenges. The centrifugal forces of raw self-interest, combined with the power of modern technology, are threatening to slowly tear civilized society apart. We can draw on the age-old, yet radically modern, wisdom of how to become sovereign masters of our own minds again. To usher in a new era of the 21st-century Humanist Renaissance, which we so desperately need, we must elevate human reason to a new level.