While many Westerners still think of yoga as an invigorating series of postures and breathing exercises, these physical practices are only part of a vast and ancient spiritual science. For more than three millennia, yoga sages systematically explored the essential questions of our human existence: What are the root causes of suffering, and how can we achieve freedom and happiness? What would it be like to function at the maximum potential of our minds, bodies, and spirits? What is an optimal human life?