Since the very beginning of human life, man has tried to identify the source of everything. “Who am I?”, “What made me?”, “Did man create the stars? If not, there must be a higher being than humans, but who?” Humans have always felt the need to rely on a higher being, a god, each culture identifying him either as one or many gods working together, but ultimately they provide protection, resources and strength to everyone and everything. But who IS God? Questions such as these prompted philosophers to ponder on the existence of a God; two of the arguments produced in reference to God’s existence shall be discussed.
The two approaches of the arguments are based around the a priori and a posteriori reasoning. An a priori argument is one where the truth of the proposition does not depend on prior experience. It relies on knowledge collected outside of our own experiences. This is said by some to be an innate knowledge. The ontological argument is based around this reasoning. The basis of the argument itself depends on one’s understanding of the nature of God. The Cosmological argument on the other hand, is a a posteriori based argument  . They argue that the truth of a proposition may only be known to be true after empirical knowledge is utilised to prove the statement true or false. 
Rene Descartes, often called the father of modern philosophy, developed Anselm’s argument, in attempting to prove God’s existence from simply the meaning of the word ‘God’. The ontological argument is a priori argument. The basis of these arguments depends upon one’s understanding of the nature of God. Anselm’s definition of God being “a supremely perfect being”, is the basis of his argument. God must be such a thing that cannot be thought not to exist if he is:
“Than that which nothing greater can be conceived”. (Anslem)
Descartes points out that if you imagine a triangle, one of its main properties is that it has three sides and three corners. These are the predicates of a triangle. Descartes expands his point, this time referring to the properties of God. If something perfect is imagined, it must be even more perfect if it was in existence. Furthermore, the most perfect thing has all properties including existence. Descartes, therefore, believes, that a supremely perfect being has all predicates. Hence, if a perfect being has all predicates one of the properties must surely be existence. Therefore, if God is the greatest conceivable being and has all qualities, he must have all predicates, one of them being existence, therefore God must surely exist. Descartes says that trying to imagine God without the predicate of existence is illogical, like imagining a triangle without three sides!
The ontological argument, in whichever version, has been the object of a great deal of philosophical criticism. Traditionally, the objection posed by the 18th-century philosopher Immanuel Kant has been thought to be one of the most decisive. Kant argued that the problem with the argument lay in its claim that existence is a predicate. (A predicate term describes something done by a subject; so, in the sentence “John is eating” the predicate “is eating” describes something that the subject, John, is doing.) Kant argued that existence cannot be a predicate because it does not add any new information to an understanding of the subject.
To be told that John is bald, that he is eating, and that he is angry is to add three things to the stock of information about him. However, to be told that he exists does not genuinely communicate something about him. Likewise with God; to state simply that God’s existence follows from thinking about him is to have said nothing other than that God exists. Kant argued that nothing of philosophical consequence has been learnt. It is for this reason that many modern-day philosophers have held the ontological argument to be in error.
In conclusion to Descartes’s argument, if the most perfect thing has all predicates, then one of those properties must be existence. God is the most perfect and flawless being, hence, he must exist.
Similar to the ontological argument, the cosmological argument, also known as the first cause argument, is a classical argument for the existence of God. However, unlike the ontological argument, it derives the conclusion that God exists from a posterior premise (with evidence), as it is based on what can be seen in the world and the universe. It points the belief that there is a first cause behind the existence of the universe.
The cosmological argument is based on contingency (dependent on something else) and points out that things come into existence because something has caused them to happen. The argument also states that things are caused to exist but they do not have to exist and that there is a chain of causes that goes back to the beginning of time. Time began with the creation of the universe, which came into existence about 15 billion years ago.
Plato argued one of the Cosmological arguments earliest forms. He argued that “the power to produce movement logically comes before the power to receive it and pass it on”  This basically means that if there if movement, then something has to have caused this. This could not logically go on for infinity, so there has to be a single solitary being that caused this chain of events. This he calls the First Mover. Aristotle also believed in the Prime mover, the uncaused cause, the original cause. In this respect the two arguments are very similar.
St Thomas Aquinas developed the cosmological argument. He developed five ways, the ‘Demonstratio’, to prove the existence of God. The first three ways forms the cosmological argument as a proof of the existence of God. These three ways are, motion or change, cause and contingency.
In the first way, Aquinas states that anything which is in motion is moved or changed by something else. The object causing this ‘push’ in movement is also given motion by another object. According to Aquinas, infinite regress is logically impossible, and because of this there must be something at the beginning which caused this motion, without being affected itself. This is God.
“It is certain, that in the world some things are in motion. Now whatever is moved is moved by another” (Aquinas – Summa Theologica  )
From this quote, Aquinas clearly points out that, an object only moved when an external force was applied to it. He continued that objects only changed because some external force had brought about the change. He spoke of things achieving their potential through an external influence. Aquinas used the example of fire making wood hot. When fire is applied to wood, it changes the wood to achieve its potential in becoming hot. Aquinas, in relation to the fire, stated that in order for a thing to change, actuality is required. If it did not, the thing would have to start the change itself, hence it would require both actuality and potential. However, Aquinas saw this as a contradiction, i.e. if wood could make itself hot then it would be hot already.
Wood cannot be hot to beginwith, otherwise it would not change and become hot. Therefore, Aquinas is emphasising the fact that wood is not hot already is its actuality.
Moreover, something must have made the fire change and come about, hence each change is the result of an earlier change. However, Aquinas reported that these early changes did not go on to infinity, so there must have been a prime mover He concluded this first mover to be no other but God.
In the second way, Aquinas says that God must be an uncaused causer, because if God were the efficient cause, and physically giving the object a ‘push’, rather than being The Final Cause, the ‘push’ would affect God, meaning it would be contingent rather than necessary. To help explain this argument of motion, Aquinas uses the idea of dominoes. One force knocking domino causes the whole line of them to fall. For the objects to go from Potentiality to Actuality there needs to be something in the beginning which has already possessed Actuality.
“aˆ¦it is necessary to arrive at a first mover, moved by no other; and this everyone understands to be God” (Aquinas)
In the third way, Aquinas brings up the point of contingency of matter in the universe. He identifies that things come in to existence but then stop existing. He states that there must have surely been a time when nothing existed, however, for these to start existing, the universe must have always existed. Aquinas states:
“aˆ¦if at one time nothing was in existence, it would have been impossible for anything to have begun to existaˆ¦therefore we cannot but admit the existence of some being having of itself its own necessityaˆ¦”
Furthermore, there must have been a ‘necessary being’ to bring about this existence, this being God. He evaluated that if God did not exist, then nothing would exist.
In conclusion, Aquinas presents in his three ways of proving the existence of God that nothing could have existed without the existence of another. Moreover, something else must have caused the existence of this cause. Hence, a chain of causes is brought about. However, Aquinas emphasises that there must a beginning to the chain of causes. If the chain of causes is finite, then it means that this being does not have to rely on anything else to come into existence. There is only one such beingaˆ¦God.