Aquinas was a philosopher and theologian who Combined the theological principles of faith with the philosophical principles of reason and was one of the most influential medieval thinkers of Scholasticism. Aquinas attempts to unify the Christian themes and concepts of Aristotelianism, he thus shared a common heritage with Islamic and Jewish philosophers and owed to Aristotle the difference between speculative science and practical science. In his first article, Summa Theologiae, he states that other than philosophic discipline, there is a need for a sacred doctrine. He explains that Christianity unlike Islam and Judaism is first and foremost a sacred doctrine or faith that demands obedience to a set of beliefs leaves it followers at liberty