Metaphysics is the foundation of philosophy. It seeks to explain everything that exists and answers the questions regarding reality. Many philosophers such as Plato, Aristotle and Aquinas all attempt to answer the fundamental questions – What is the nature of ultimate reality? Why is there something rather than nothing? & Does God exist? However, this essay will only be taking a look at the philosophical principles and methods of Aristotle and St.Thomas Aquinas, through comparison and contrast. Both philosophers made a contribution to the concept of metaphysics, each with similar and different ideas/views on Natural Law and the existence of God. In a way, Aristotle and Aquinas go hand-in-hand, Aristotle provides the framework for these principles and Aquinas explains how the theories are tied Catholic doctrine. The customs that informed the philosophy of Aristotle and Thomas Aquinas is their pasts. Aristotle was born in Greece, he lived from 384-322 BCE. At 17 he travelled to Athens to study under Plato, which he did for about twenty years. After Plato died, he left Athens and became an educator to Alexander the Great. Following Alexander becoming king, Aristotle returned to Athens where he established his own school. However, was later banned from this city due to his ties to Alexander and the Macedonians. As for Thomas Aquinas, he was born in 1225 between Rome and Naples. He received his education at the monastery of Monte Cassino and against his parents wishes he entered the Dominican order of priests. Aquinas was sent to Paris and Florence where he was a teacher, and during this time found Aristotle’s philosophical writings and was immensely influenced by them. His analysis on Aristotle’s Metaphysics is a magnificent explanation of what was written by the philosopher and he used it to defend many Catholic beliefs. In 1323, he was officially declared a saint in the Roman Catholic Church. Aristotle referred to metaphysics as “first philosophy” and was credited as the first philosopher to contribute to metaphysics. Many philosophers frequently evolve the ideas of their predecessors. A prime example is Thomas Aquinas, who drew from numerous of Aristotle’s writings. These philosophers are identified as leading contributors to Natural Law. The theory of Natural Law is interested in the issues concerning moral obligations. Aristotle is known for developing the first theory of Natural Law. Both Aristotle and Aquinas discussed law in relation to morality, justice, and ethics, but Aquinas adjusted his analysis to Catholic beliefs. It can be said that Aquinas’ theories are Aristotelian ideas merely made suitable to apply to Christian content. Nicomachean Ethic and The Politics are some of Aristotle’s works that highlight the connection between legal and political philosophy. Aristotle indicated in Nicomachean Ethic that law supports an ethical life, which builds the ‘perfect community’. He also suggested that people should “behave in a way that is consistent with a virtuous existence,” He illustrated justice as “a state of mind that encourages man to perform just actions”, by just, he means ‘lawful’ ‘impartial’ and ‘righteous’. In The Politics, Aristotle developed an approach called theology which is a form of reasoning. It helped him comprehend which natural human inclinations are ‘good’. Also, in his book he expressed that in order for people to obtain happiness and virtue they needed to participate in the life of the polis (city state) and for Aristotle, people attain their greatest potential by connecting with others for the good of everyone. Thomas Aquinas defined his theory of Natural Law in Summa Theologiae. He developed three types of law. In Divine Law he stated that human beings are naturally inclined towards integrity and decency. According to Aquinas, the objective of law is to encourage good and human’s ‘good’ tendencies are to protect life, procreate, be apart of society and know God. He proposed that the Church had the final say on natural law, which was essentially acquired from God. Without a doubt, Aquinas was greatly influenced by the work of Aristotle. Aquinas agreed with Aristotle that human beings will only gain virtue when they are part of society. Also, both state that the purpose of law is to promote good. Yet, Aquinas’ Catholic background had more of an influence on his theory of Natural Law than Aristotle’s philosophy. Aquinas goal was to make God the center of his philosophy while Aristotle’s was to construct a ‘perfect community’ using reason.