In the ancient world, the existence of god has been a question that a lot of different scholars pondered about. Augustine brought up the question about the presence of evil within the world if God were, in fact, all good. Then, Thomas Aquinas brought forth several proofs for and against the existence of God. He even went on to state that he could demonstrate to a live audience that God’s existence (not essence) was absolute. Aquinas perfected the grand “medieval synthesis” of faith and reason, and the Catholic church canonised him.
Thomas Aquinas differentiated essence and existence in De Ente Et Essentia. The mere concept of what something is doesn't necessitate it exists in real life. I can think, even talk, about fairies or any of the mythical creatures without them roaming the earth. This distinction was also an ingenious argument for God. Aquinas stated that while we can determine the existence of the Sun, we do not know what it’s essence is. Similarly, God’s essence was not needed to establish God’s existence. So, having the definition of a word gave a better understanding of the defined word’s existence. The essential characteristics of an entity are those things that define it and without which it ceases to be the same thing. Essence is not such a necessary issue in ontology now as it was in the middle ages say.
However, there were several others, including, William of Ockham, who did not see the ‘sense’ in Aquinas’ ideas. Ockham went on to refute Aquinas’ proofs of God’s existence through logic and reason. This, however, meant that he was in danger of hearsay and had to face the wrath of the Catholic Church. While, Thomas believed that theology could be said to be a science in the classical Aristotelian sense because (more or less) it began with first principles and reasoned logically out from there, William of Ockham disagreed, since the first principles themselves could not be proven "from any necessary laws that human logic or rationality can uncover.”
Ockham believed that Aquinas had inadvertently demystified God with reason, and mystified nature while he tried to understand God using science. Instead, what needed to happen, according to Ockham, was to re-mystify God and demystify nature. He said that we could not explain divinity with human concepts and that it would be impossible for someone to try and understand God’s existence, and that it could only be found in faith, not science. Ockham’s Razor had brought about the beginnings of nominalism and refuted the dogma of the time.
Of course, today, scientists have discovered new pieces of information through logic and reason. Discoveries have been made in the field of biotechnology, astrophysics and even witnessed evolution before our very eyes. Within Aquinas’ five proofs of God’s existence, it is possible to refute his ideas with science, logic and reason.
Argument from Motion: "Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God." It rests on the intuition that the universe is changing. Who says if things change they must be changed by something else? Why must a prime mover be "God"? For example, when an apple falls, gravity causes the apple to fall. In this sense, God is not the thing that moves these items but the scientific phenomenon of gravity.
Efficient/First Cause: "Nothing is caused by itself. Every effect has a prior cause. This leads to a regress. This has to be terminated by a first cause, which we call God." This argument requires that tensed facts objectively exist. In modern Physics, the B or C Theories of Time both posit that tensed facts are mere illusions and don't objectively exist. It's just moving the causation issue up a step. What caused God? Say that God always existed then, the logical conclusion would be that the Universe always existed and that there's no need for creation if it was already here. Does it mean that the universe is causeless?
Cosmological argument: "Nothing is caused by itself. Every effect has a prior cause. This leads to a regress. This has to be terminated by a first cause, which we call God." This argument is weak because time in this universe has a beginning- The big bang. Yes, events before the big bang are currently unknown. Just like one cannot prove that 'God' didn't start our universe's big bang, one can also not prove that aliens didn't start our big bang. There are lots of theories here, but so far nothing we can prove.
Argument from Gradation: "But we judge these degrees only by comparison with a maximum. Humans can be both good and bad, so the maximum goodness cannot rest in us. Therefore there must be some other maximum to set the standard for perfection, and we call that maximum God." We can tell which of two objects is longer or bigger, mathematically, by seeing which is more than the other: we take one as standard and compare if the other is above or below that standard. But, there is no guarantee that a maximum is logically possible, as in the cases of length or magnitude.
Also, why must a 'perfect' version of something necessarily exist? Everyone has a different perspective on everything. What one person sees may have a different meaning to another person. For example, I may find a book to be amazing, but my friend may not have enjoyed it. In this sense, it is possible to see God as not perfect and may see something else as a perfect being.
Argument from Design: "Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.” We can also argue that if we apply this to God, the case falls apart, or God has a cause. If everything in the universe was designed, it is also impossible to establish a distinction between designed and non-designed objects, because there are no non-designed objects for us to experience!
Why can't a spontaneous event cause something to move in a consistent pattern? Mainly when things have to follow the laws of physics, some things are going to have to move in a logical way like in the case of orbits. Aquinas stated that the symmetry of the world was far too high to be coincidental, and therefore must have been placed by some higher being. However, while, the design of the universe does declare the existence of the designer, we have no proof of who or what designed the universe. We have no evidence of whether it was God, or something else.
It can be seen from all these aspects that the existence of God is challenging to determine and both Aquinas and Ockham put up excellent battles to demonstrate God’s existence. Aquinas used metaphysics to create a sophisticated idea dealing with God’s presence, but Ockham refuted it merely with faith. However, neither demonstrates God’s existence and we must now determine a better approach to prove God’s existence, that is if God truly exists.