I am sick with a headache – but not because of this…

Faith versus Reason

A discourse on St. Thomas Aquinas and St. Anselm of Canterbury

Jediah L.


Sunday, January 27, 2008

The two names, St. Thomas Aquinas and St. Anselm of Canterbury carry great weight in both the world of religion and philosophy. In this introduction to philosophy course, we have been asked to compare and contrast the Ontological argument of Anselm to the arguments of cosmology from St. Thomas Aquinas. While we can find cosmological arguments in works of Anselm (like those put forth in the Monologion), and we can find ontological arguments by Aquinas (like some of the divine traits put forth in the quinquae viae), the intent of this assignment is not to limit either philosopher to a specific set of arguments, rather to compare and contrast these identified arguments for the existence of God. As a result, in this paper, we will focus specifically on the differences of the ontological versus cosmological arguments of the two aforementioned philosophers. Our primary focus will be to show how each proof presents a priori or a posteriori arguments for God’s existence, as well as compare and contrast the way of faith and reason shown by the differing methods of these two arguments.

We turn our view first to St. Anselm of Canterbury. Anselm, in his ontological argument, argues first and foremost of the a priori nature of God, that is, that the existence of God is necessary and self-evident. His philosophical proof can be defined in its essence as thus:

1. God by definition is that which no greater can be conceived

2. That which is outside of the mind is greater than that which is only inside of the mind (for existence is greater than non-existence).

3. If God existed only inside of the mind, than one could conceive of a God greater than God

4. Therefore: God exists (outside of the mind)

In the Proslogium Anselm lays out this argument, and asserts that even the fool can be convinced that there is in understanding, that which no greater can be conceived. His proof continues to dictate that while the fool might state, that which no greater can be conceived only exists in understanding, it by necessity must also exist in reality, for if it is conceived in understanding alone, it can also be conceived to exist in reality (which is greater), and by definition that which no greater can be conceived is that which no greater can be conceived..:namespace prefix = w ns = “urn:schemas-microsoft-com:office:word” /> (Pojman, Philosophy: The Quest for Truth, 2006). While this reasoning seems very circular, the Theologian and Apologist Cornelius Van Til points out that “every system of thought is circular when arguing its most fundamental presuppositions (e.g. a rationalist can defend the authority of reason only by using reason) (Frame).”

One of the primary points to notice of Anselm’s argument is that it defines the existence of God as a necessary and analytical truth and then builds rational arguments upon that. This thought process can be seen in Anselm through one of his famous phrases: Credo ut Intellegam. This phrase acts in summation of the idea that we first have faith in what necessarily has to exist by definition, and through this faith we seek the rationale (understanding) of this faith (faith comes before reason).

The arguments by St. Thomas Aquinas, however, take a different approach to proving God. Aquinas uses a posteriori reasoning; that is, he seeks to prove God by contingent and synthetic truths through particular experiences and justifications. Of the five proofs, the two that are given the most attention in our assigned readings are the arguments of first cause and arguments of contingency.

The first cause argument goes something like this (Pojman, Philosophy : The pursuit of wisdom, 2006):

1. There exists things that are caused

2. Nothing can cause itself

3. An infinite number of causes cannot be regressed

4. Therefore there exists an uncaused first cause

5. This uncaused first cause is God

This argument is based on an understanding of ex nihilo nihil fit, which is to say, out of nothing, nothing comes. The idea behind this understanding is that in order for something to create itself (to cause itself), it must predate itself, and therefore it must exist and not-exist at the same time, which is not logically or casually possible and violates the law of non-contradiction put forth by Aristotle. Secondly, premise three can be furthered through a thought experiment proposed by David Hilbert, referred to as Hilbert’s hotel. This experiment shows the absurdity of trying to traverse an actual infinite, and draws a differentiation between an actual infinite and a potential infinite, the later being an indefinite collection. In this thought experiment, Hilbert’s hotel has an infinite number of rooms, but an infinite number of guests as well (therefore the hotel is full). Hilbert shows that you can still add an infinite number of hotel guests (even though the hotel is already full), and yet have no more guests then before you added the infinite number of guests. His conclusion is that the hotel has a potential infinite (an indefinite collection) rather than an actual infinite (Pojman, Philosophy : The pursuit of wisdom, 2006).

The contingent argument goes something like this (Pojman, Philosophy : The pursuit of wisdom, 2006):

1. Every being that exists is either contingent or necessary

2. Not every being can be contingent

3. Therefore there exists a necessary being upon which the contingent beings depend.

4. A necessary being on which all contingent beings exist is what we mean by “God”

5. Therefore God exists

This argument is also similar to the first cause argument, in that it describes the concept of ex nihilo nihil fit, that is, before contingent beings come to exist, there must be something non-contingent (therefore necessarily existing) to predate those things that are contingent, because contingent things cannot create themselves, and are contingent in reference to something outside of themselves.

As can be seen in these cosmological proofs, Aquinas, unlike Anselm’s ontological argument, takes the approach that we can come to faith in the existence of God, first by reasoning through our experiences and through rational justifications.

In summary, both Thomas Aquinas and St. Anselm agree in the existence of an omnipotent, omnibenevolant, omniscient God, the God of the Christian Bible, however, they approach the subject within these discussed proofs quite differently. Aquinas uses a posteriori reasoning based on contingent and synthetic truths defined through particular experiences and justifications, his idea is that logic and reason will bring us to the knowledge of the existence of God. Anselm, on the other hand, uses a priori reasoning based on necessary and analytical truths, his premise is that we start our search for God with faith in what is necessarily true, and use that faith to bring rationale to our understanding.


Frame, J. M. (n.d.). Van Til, Cornelius (1895-1987). Retrieved January 27, 2008, from The Works of John Frame and Vern Poythress: http://www.frame-poythress.org/frame_articles/2005Vantil.htm

Nolan, L. (2006, October 18). Decartes’ Ontological Argument. Retrieved January 27, 2008, from Stanford Encyclopedia of Philosophy: http://plato.stanford.edu/entries/descartes-ontological/

Pojman, L. P. (2006). Philosophy : The pursuit of wisdom. Belmont: Holly J. Allen.

Pojman, L. P. (2006). Philosophy: The Quest for Truth. New York: Oxford University Press.

Second portion of our assignment is to use the Hypothetical syllogism pattern to show how Descartes’ ontological argument can be expressed. Taking Descartes’ ontological argument by way of a quote from the Fifth mediation (Nolan, 2006), my hypothetical syllogism for the ontological argument would appear as such:

1. If I can clearly and distinctly relate a property to an object then I must have some foundation to understand the property of the object

2. If I have a foundation to understand the property of an object then the object must have that property

3. Therefore: If I clearly and distinctly relate to the property of an object, then the object must have that property

4. I can clearly and distinctly relate existence to God, therefore God must have existence