This chapter details the four cardinal virtues, described as the foundational “hinges” (cardo) upon which a flourishing moral life is built: Prudence, Justice, Fortitude, and Temperance. Drawing from St. Thomas Aquinas, it defines each virtue’s unique role. Prudence is the “charioteer,” guiding our actions with right reason. Justice perfects the will to give God and neighbor their due. Fortitude provides the courage to face difficulties and endure in pursuit of the good. Temperance brings moderation and balance to our desires for pleasure. The chapter emphasizes that these virtues are interconnected, with prudence uniting and directing the others, highlighting that moral excellence requires a holistic character. Finally, this classical wisdom is connected to contemporary insights from psychology and neuroscience, underscoring the timeless relevance of the cardinal virtues for achieving a well-ordered and truly human life.