The four Stoic virtues — courage, temperance, justice, and wisdom — are independent yet inseparable. You can't be truly courageous without wisdom to know what to be courageous about, or just without the discipline to follow through. They're not a checklist but an interlocking system. These are also the cardinal virtues of Christianity, where 'cardinal' means 'hinge' — the pivotal framework on which a good life turns.