The existence of God and the understanding of who God is has dwelt in the mind of man since the beginning of time. We see this in our history books when we see the various pagan, polytheistic religions of the ancients; and we see it in various world religions of today. Yet, the question still nags at us, goading us on in hot pursuit of the truth. Is there a God? And if so, who is He? These are some of the most fundamental questions that man must ask himself, and these are the basis for all Christian Theology.In the late thirteenth century a man by the name Thomas Aquinas sought to answer this most fundamental question in his work the Summa Theologiae. The Summa is separated into three parts, the first dealing with God, the second man, and the third Jesus Christ, the God-Man. We will be dealing with the first part. Before he even touches on the more theological arguments for who and what God is, Aquinas sets out to establish a convincing argument of how man can, by reason, come to know of God’s existence. To do this Aquinas proposes a variety of questions. One of the questions he presents is the question of whether or not the existence of God is self-evident. This question doesn’t deal with Who God is, but rather it addresses the issue of whether or not man is able to come to the knowledge that God does exists, even if that knowledge is not a perfect knowledge of who God is, which Aquinas says is not known to man naturally.

Aquinas states that things can be self-evident in one of two ways, either it is self-evident in itself and to us, or self-evident in itself and not to us. To illustrate what this means, he gives us an example of something that would be self-evident in itself and to us, his example being that “man is animal.” This holds true because animal is in the essence of man, meaning that the nature of animal is in the nature of man. Of course, we would have to further extrapolate what this means, after all, aren’t men at a higher level of being than the beasts of the field? I answer that: Man is a composite being of body and soul, but the nature of animal can be equated to man in that the nature of man is one of flesh, blood, bone, and sensory capability, which would equate the nature of animal being composed of flesh, blood, bone, and sensory capability. That is to say, since both man and animal share the common nature of flesh and blood, man is animal; but since man is at a higher level of being than the beasts of the field, namely in that we posses the immortal soul, free will, and intellect, animal cannot be man. The conclusion that Saint Thomas Aquinas eventually comes to is this: God is not self-evident to us, but only in Himself, because we do not know the nature of both the predicate and the subject.

Therefore I say that this proposition, God exists, of itself is self-evident, for the predicate is the same as the subject, because God is His own existence as will be hereafter shown. Now, because we do not know the essence of God, the proposition is not self-evident to us, but needs to be demonstrated by things that are more known to us, though less known in their nature – namely, by His effects. (Saint Thomas Aquinas, Summa Theologiae)

With the assertion that “man is animal” we know both the predicate and the subject, we know what man and animal are, so we can make this argument. When it comes to God, however, we don’t know both the predicate and the subject in question. Aquinas informs us that God is His own existence, that is to say that God’s essence equals God’s existence. While God’s nature is most perfectly intelligible, rational, and clear, our minds are not proportioned to comprehending the immensity of God; rather, it is much more proportioned to comprehending the nature of a creature, which is a mixture of both form and matter. In the same sense, 4/2=2 is much easier to comprehend than say ∞/2=∞, because while the division of an infinitely large number by an infinitely smaller number is much simpler mathematically, our minds are not accustomed to comprehend the gravity and immensity of infinity, whereas with 4/2=2 we are much more accustomed to say that 2 is half of 4. The only way we are able to grasp this concept of ∞/2=∞ is if someone were to first explain to us what infinity was, where with the numbers 4 and 2, we learned them as small children and integrated them into our knowledge of the way the world works through experience, such as dividing four donuts between you and a friend only leaves you with two left; whereas we have never experienced infinity in our daily lives, as we cannot have an infinite amount of donuts.

When investigating the question further, one can run into what appears to be some difficulties. With Paul’s letter to the Romans, for instance, in chapter one, verse twenty, we hear him state, “Ever since the creation of the world His invisible nature, namely, His eternal power and deity, has been clearly perceived in the things that have been made.” Also, with Saint Augustine, we see him issue this challenge:

Question the beauty of the earth, question the beauty of the sea, question the beauty of the air distending and diffusing itself, question the beauty of the sky… question all these realities. All respond: “See, we are beautiful.” Their beauty is a profession [confessio]. These beauties are subject to change. Who made them if not the Beautiful One [Pulcher] who is not subject to change.” (St. Augustine)

These proclamations by two of the greatest Saints of the Church seemingly, and that’s the key word, do away with Saint Thomas’ whole argument. However, one could make the argument that upon examining Saint Paul’s letter a little more closely, one could draw out and state that when Paul says, “namely, his eternal power and deity,” he could be saying that all of creation points towards the creator and his deity simply as a creator that must exist, and not revealing his exact nature, which can only come from Divine Revelation. The same argument could be made for Augustine, saying that while creation is beautiful and reveals a deity that must be beautiful as well; the true, personal, relational nature of God is not self-evident. Aquinas also addresses this, to an extent, in his reply to the first objection of the argument he proposes in the Summa, which states that knowledge of God exists naturally in us, and things said to exist naturally in us are self-evident to us. Aquinas says:

To know God exists in a general and confused way is implanted in us by nature, inasmuch as God is man’s beatitude. For, man naturally desires happiness, and what is naturally desired by man is naturally known by him. This, however, is not to know absolutely that God exists; just as to know that someone is approaching is not the same as to know that Peter is approaching.” (Thomas Aquinas, Summa Theologiae)

So, while the existence of God may be inferred naturally and may even be known naturally, that is not to say that the essence of God is known naturally or even self-evident. All in all, bearing the possible objections and their refutations in mind, Aquinas’ argument that the existence of God, that is to know God in His entirety, is not self-evident  is solid with a firm base in Theology and Philosophy. And it is because of this, that it is so necessary and essential that we read the Word of God in Sacred Scripture, for as St. Jerome says, “Ignorance of Scripture is ignorance of Christ,” and that just simply will not do. Along with His Divine Revelation, God has given us an intellect to rationalize and to explore and study the beautiful world around us so that, by doing so, we will be able to come to a much fuller and intimate understanding and contemplation of God and His majesty.


(Thomas Aquinas. Summa Theologica. In Classics of Philosophy, edited by Louis Pojman and Lewis Vaughn, 256-257.)

(Peter Kreeft. A shorter Summa., 48. San Francisco: Ignatius Press, 1993.)

(Didache Bible: With Commentaries Based on the Catechism of the Catholic Church, 2nd Catholic ed., 1510. San Francisco: Ignatius Press, 2015.)

(Catechism of the Catholic Church, 2nd ed., 32.)

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