The Summa Theologiae (Latin: Compendium of Theology or Theological Compendium; also subsequently called the Summa Theologica or simply the Summa,) is the best-known work of Thomas Aquinas and (although it was never finished) arguably "one of the classics of the history of philosophy and one of the most influential works of Western literature". It was intended as a manual for beginners and a compilation of all of the main theological teachings of the time. It presents the reasoning for almost all points of Christian theology in the West by medieval scholastic reckoning. The Summas topics follow a cycle: the existence of God; God's creation, Man; Man's purpose; Christ; the Sacraments; and back to God. It is famous for its five arguments for the existence of God, the Quinque viae (Latin: 5 ways). Throughout his work, Aquinas cites Augustine of Hippo, Aristotle, and other Christian, Jewish, Muslim & ancient pagan scholars Theology is the most speculative of all the sciences since its source is divine knowledge (which cannot be deceived), and because of the greater worth of its subject matter, the sublimity of which transcends human reason. When a man knows an effect, and knows that it has a cause, the natural desire of the intellect or mind is to understand the essence of that thing , natural, because this understanding results from the perfection of the operation of the intellect or mind. The existence of something and its essence are separate. That is, its being and the conception of being man has or can imagine of it (for example, a mountain of solid gold would have essence , since it can be imagined , but not existence, as it is not in the world) are separate in all things except for God, who is simple. The existence of God, his total simplicity or lack of composition, his eternal nature ("eternal," in this case, means that he is altogether outside of time; that is, time is held to be a part of God's created universe),