One of the most commonly pondered philosophical questions is the mystery of the universe's origin. For countless centuries mankind has speculated as to how and why the universe as we know it came into existence. Unfortunately, in attempting to answer this question, we simply raise more questions; each as unanswerable as the last. For instance, in asking where the universe came from, many have applied the cosmological argument to arrive at the conclusion that God must have imposed His creative influence. However, for other philosophers this poses the equally perplexing question as to how God achieved existence. Consequently, the question has to be asked; must there be a first cause of everything While considering the topic of causality, it would be beneficial to investigate the ideas of two of the leading philosophers in this area; Saint Thomas Aquinas and David Hume.

While Aquinas attempts to prove the reality of a finite chain of causality and hence an initial cause, Hume argues against trusting implicitly our perception of causality. Through his examination of the cosmological argument concerning the existence of God, Aquinas was able to validate and support his refutation of a causal series continuing infinitely into the past. Essentially, Aquinas succeeds in justifying that the universe has a definitive beginning and proceeds to explain the necessity of God as the agent of this beginning. For the purpose of understanding Aquinas' argument, causality can be defined as the relationship between two consecutive events and the presumption that one always precludes the other and in fact brings it about. What Aquinas' argues is that in order for an event to happen, a force must be applied by something else.

Aquinas uses the analogy of a stick moving something only if a hand moves the stick. However, he contends that this series of cause and effect cannot go back into an infinite past. According t his Summa Theological, Aquinas reasons that " this cannot go back to infinity. If it did, there would be no first cause of change and, consequently, no other causes of change-for something can be a secondary cause of change only if it is changed by a primary cause." Essentially Aquinas argues that to remove a cause, is to also remove its effect. Therefore, by removing the initial efficient cause, all resultant intermediary causes are also removed. This would also negate the possibility of any final cause.

Aquinas' argument at this point appears to be logically sound insofar as providing a satisfactory justification for a primary initial cause. However the question still remains of what this initial cause was and the justification for its independent existence outside the laws of causality. Inseparably linked with his proposition of a finite chain of causation are Aquinas' arguments proclaiming the existence of God who he introduces as the literal "First Mover" or initial cause. However many philosophers have disagreed with Aquinas' proclivity towards this cosmological style of argument and see it as superficial answer to the problem of how the universe was set into motion.

In response to Aquinas' proposition of God as the initial cause, a common response is that this only moves the causal series back one step. Consequently it can be argued that Aquinas fails to identify the initial cause, leaving only another equally perplexing question; what created God In retaliation, Aquinas further develops this cosmological style argument by explaining qualities of God to circumvent this objection. Basically Aquinas defence revolves around God being outside time and space. Similarly He possesses a quality of infiniteness that transcends these restrictions; "He is without beginning and end, and has all His being simultaneously; and in this consists the notion of eternity." Expanding on this, in accordance with his theory of causality, Aquinas affirms that there are possible and necessary beings. In nature it is always possible for things to exist or not exist. These things are referred to as possible or contingent because they are not required to exist.

Contingent beings must derive their existence from something that has its existence necessarily in itself. Everything exists because of the mover or creator, however the First Mover (God) can only start this series of creators. Therefore in order to exist independently Aquinas characterised God as a necessary being. Hence God is the only necessary being and also not subject to the constrictions of causality. Aquinas shows that a necessary cause by nature would retain a characteristic of independence from the normal chain of causation.

This description of an initial cause, could be seen to correspond to recent advances in theoretical physics. At the time prior to the big bang, the universe was supposedly compressed into a point of infinite density, with infinite space-time curvature. This is what is referred to as a singularity, and retains a property of existing as a point where the normal laws of physics break down. This concept can be construed by philosophers as an event that exists independently of the laws of physics and therefore possibly independent of the laws of causality. A singularity could be a modern version of Aquinas' original necessary cause. Despite his success, Aquinas' arguments can be said to rely too heavily on our sensory perception of the world.

Hume developed arguments against unconditionally trusting our perception of causality. These arguments state that because event 'A' is always observed directly before event 'B' it is assumed that this is a cause and effect series. Hume reasons that there is no object that implies the existence of another when the objects are considered individually. Hume referred to the causal principle as simply a "habit of association" produced by the mind when it observes repetition of instances 'A' determining 'B.' This method of thought could also provide a solution for the problem of initial cause. For example, Hume argues that it is entirely possible that events can happen independently of each other. By this logic, it would not be difficult to view the creation of the universe not as the initial cause, but an event (as with all other events) independent of a cause.

Finally, it can be seen that there is a strong argument denying the possibility of an infinite series of events extending back into the past. If the theory of a first cause for everything is to be accepted, it appears that this cause would have to exist independently of the laws of causality. Alternatively, the assumptions we make about the nature of these causal laws are false.