Among all human knowledge, the understanding of oneself is the most important and has the greatest influence on one's existence as well as on one's actions and decisions. It forms the basis of one's education or the appropriate physical and mental training for one's purpose, the preservation of one's temporal life, health, and all laws of human society. Therefore, throughout history, thoughtful individuals have strived to understand human abilities and inclinations and to guide them for the greater good. Thus, educators found ways to develop human potential for their purpose, and legislators established laws to give proper direction to the inclinations of individuals living in society. Meanwhile, the ever-active and perfection-seeking spirit of inquiry in humans did not stand still, as it investigates the fundamental causes of all nature.