Fridays with Aquinas: Can it be Demonstrated that God Exists

Article 2. Whether it can be demonstrated that God exists?

Objection 1. It seems that the existence of God cannot be demonstrated. For it is an article of faith that God exists. But what is of faith cannot be demonstrated, because a demonstration produces scientific knowledge; whereas faith is of the unseen (Hebrews 11:1). Therefore it cannot be demonstrated that God exists.

Objection 2. Further, the essence is the middle term of demonstration. But we cannot know in what God’s essence consists, but solely in what it does not consist; as Damascene says (De Fide Orth. i, 4). Therefore we cannot demonstrate that God exists.

Objection 3. Further, if the existence of God were demonstrated, this could only be from His effects. But His effects are not proportionate to Him, since He is infinite and His effects are finite; and between the finite and infinite there is no proportion. Therefore, since a cause cannot be demonstrated by an effect not proportionate to it, it seems that the existence of God cannot be demonstrated.

On the contrary, The Apostle says: “The invisible things of Him are clearly seen, being understood by the things that are made” (Romans 1:20). But this would not be unless the existence of God could be demonstrated through the things that are made; for the first thing we must know of anything is whether it exists.

I answer that, Demonstration can be made in two ways: One is through the cause, and is called “a priori,” and this is to argue from what is prior absolutely. The other is through the effect, and is called a demonstration “a posteriori”; this is to argue from what is prior relatively only to us. When an effect is better known to us than its cause, from the effect we proceed to the knowledge of the cause. And from every effect the existence of its proper cause can be demonstrated, so long as its effects are better known to us; because since every effect depends upon its cause, if the effect exists, the cause must pre-exist. Hence the existence of God, in so far as it is not self-evident to us, can be demonstrated from those of His effects which are known to us.

Reply to Objection 1. The existence of God and other like truths about God, which can be known by natural reason, are not articles of faith, but are preambles to the articles; for faith presupposes natural knowledge, even as grace presupposes nature, and perfection supposes something that can be perfected. Nevertheless, there is nothing to prevent a man, who cannot grasp a proof, accepting, as a matter of faith, something which in itself is capable of being scientifically known and demonstrated.

Reply to Objection 2. When the existence of a cause is demonstrated from an effect, this effect takes the place of the definition of the cause in proof of the cause’s existence. This is especially the case in regard to God, because, in order to prove the existence of anything, it is necessary to accept as a middle term the meaning of the word, and not its essence, for the question of its essence follows on the question of its existence. Now the names given to God are derived from His effects; consequently, in demonstrating the existence of God from His effects, we may take for the middle term the meaning of the word “God”.

Reply to Objection 3. From effects not proportionate to the cause no perfect knowledge of that cause can be obtained. Yet from every effect the existence of the cause can be clearly demonstrated, and so we can demonstrate the existence of God from His effects; though from them we cannot perfectly know God as He is in His essence.

What do you think?

19 Responses to “Fridays with Aquinas: Can it be Demonstrated that God Exists”

  1. I appreciate Aquinas very much. He was truly a theological titan in the history of the church.

    However, I think he would have done well to finish the verse to which he refers. Romans 1:20 continues: “So they are without excuse.” This would have added a precision to his thinking that is missing.

    Through the Nature-Grace paradigm he interprets Paul’s words “being understood” to mean “being able to be understood.” In other words, he begins with the assumption that man is able to reason “naturally” apart from an immediate work of divine grace, and therefore supposes that man somehow stands outside the very revelation that he is trying to understand.

    Paul on the other hand seems to be communicating an immediate knowledge of God’s existence when he says, “So they are without excuse.” In other words, Paul seems to be saying God has revealed himself in his creation, of which we are a part, therefore we all know immediately that God exists by virtue of our being revelation from God (i.e. created). This immediacy of theological knowledge doesn’t abrogate a mediation of knowledge with respect to other aspects of God besides his existence, but it does expose a fatal flaw in the Nature-Grace Paradigm. In order for the paradigm to work, it must be true at its most fundamental level (i.e. at its starting point). But if we allow for immediate knowledge of God according to his grace in general revelation (i.e. nature), then we deny the starting point for the nature-grace paradigm, and therefore deny the paradigm.

    I think a better paradigm is the “general revelation-special revelation” paradigm, which is closely related to the “common grace-special grace” paradigm. This is the paradigm from which Calvin later works in the Institutes.

  2. Jay, that is interesting. Sounds like a presuppositional perspective, of which Aquinas was not!

    However, I have never seen any exegetical commentator take the direction you have. It would seem that “being understood through what has been made” cannot be taken in the way you have suggestion. Do you have any more info?

  3. Micheal, I’m confused. Could you elaborate on your question?

    (And I am a presuppositionalist, in the vein of Van Til, Frame, et. al.)

  4. Michel,

    I think the arguments from Natural theolgy are valid and do prove the existence of a higher intelligent Etity who evidences intelligence, personality, et al. I don’t think that Aristotles’ impersonal “unmoved moveris a viable understanding based on the evidence whether demonstrated a priori or a posteriori.

    Aquinas went too far in making his argument demonstrate the God of the Bible, although He (God) can only be the Entity which the evidence demonstrates. Faith and the objective revelation /the Bible are still unavoidable, for they reveal who this Entity/person is, what His name is, and what He requires.


  5. Vlad,

    I can hang with that. Good comments.

  6. Vlad,
    You sum up my thoughts, and that’s why I commented “Nein!” in the first comment. Natural theology can be assuring to those who already know special revelation, but without the Jesus Christ, the Word of God speaking to us personally then natural theology is useless.

  7. If God is Wholly Other from the universe, then there can be no necessary connection between the two which is to say that what can be reasoned from one cannot be simply applied to the other. It cannot be argued from the nature of God that he could not have made the universe differently than he did nor can it be argued from the creation that it must have a creator (unless you first begin by calling it “creation”). The acceptance of the view that there is one who created all that we experience is a presupposition which cannot be proven. On the other hand, it cannot be proven from the things that are seen and an observance of the their functions that matter and its laws are simply eternal, there is no such creator. Either is a presupposition with which one considers the universe.

    The two presuppositions produce differing views of man’s place in the universe and of the universe itself. On the one hand, if there is a God who created the universe and who cares for his creation, then man has a reason to hope for the future. On the other hand, if there is only eternal “matter” and its forces from which the universe began by a “big bang” and through evolution resulted in man, these same laws would seem to result in a lack of purpose since at some point the bonds which cause the universe to cohere together as a universe will become too weak to stop its expansion so that it will die in cold and darkness. I am an optimist. I think that there is yet a purpose and a future for man though I have no detailed conception of what that may be and can only trust in the love of God that it will be good. The other view reminds me of the closing lines of T. S. Eliott’s poem

    “This is the way the world ends,
    This is the way the world ends,
    This is the way the world ends —
    Not with a bang, but a whimper.”

    How depressing.

  8. If we accept the position that the universe began to exist then there are two possibilities.

    1. That the universe was brought into existence by another.

    2. That the universe brought itself into existence.

    Option 2. leads us to a violation of the law of non-contradiction as for an object to bring itself into existence requires it to exist (in order to be the bringer) and not exist (in order to be brought) at the same time.

    Option 1. does not automatically fail the logical test and so we proceed further.

    3. The bringer possesses volition.

    4. The bringer possesses no volition but acts as a result of natural processes.

    I have difficulties with Option 4. because natural processes themselves arise within the universe. I don’t see them leading to the universe. If that is the case then we are in the same boat as option 2.

    Option 3. allows for there to be a point at which the universe doesn’t exist, before an act of volition brings it into existence.

    If the bringer of the universe into existence possesses volition then the bringer probably possesses a degree of consciousness in order to “choose” to bring the universe into existence. If the bringer possesses consciousness then it is likely to be a “being” of some description.

    That might need some cleaning up, but I think I have shown that it’s reasonable to assume that the cause of the universe is itself a conscious being.

  9. Jason,

    Why not speak more simply? One needs a sufficient cause to produce a given effect. The argument from design is illustrated by the fact that we as humans have two sets of teeth embedded in our heads even before we have need for them. This evidences intelligent forethought and design.


  10. Jason wrote:

    Option 2. leads us to a violation of the law of non-contradiction as for an object to bring itself into existence requires it to exist (in order to be the bringer) and not exist (in order to be brought) at the same time.

    This is not quite the case. That an object existed in another state does not mean that it also did not exist “in order to be the bringer.” It simply indicates that it did not exist in it subsequent form. You simply cannot prove that God exists (which is actually a denial of God). To say that God exists is a denial of God since it considers God to arise out of, and therefore be connected with, the universe. Since God created (and creates) the universe, this is heresy.

  11. Gfsomsel. To say that the universe could have existed in another state is no answer. In what state did it exist? In a state of existence, or of non-existence?

    The argument is that if we accept the position that the universe began to exist we arrive at the second argument. You want to go back to the first assumption and suggest that the universe need not begin to exist. I would point out that what we know of the laws of thermodynamics strongly suggests that if a universe had continued to exist eternally all available energy would have been depleted. Since that is not the situation we find ourselves in it is reasonable to assume that the universe is not eternal and therefore had a beginning.

    Moreover I did not claim it “proved” the existence of God. What I was saying was that based on the evidence in front of us it is reasonable to assume there is a creator.

    Thank you Vladimir. Yes, argument from adequate cause is where I was going. Sometimes I get carried away with my own verbosity.

  12. Jason wrote:

    Gfsomsel. To say that the universe could have existed in another state is no answer. In what state did it exist? In a state of existence, or of non-existence?


    In a state of superdense matter which then exploded flinging matter outward to form the universe.

    While I personally accept the creation of the world by God, I do not think one can in any sense prove the “existence” of God. One could posit that matter always was and not be any more nor any less consistent than beginning with God. It is no less problematic to begin with God as eternal.

  13. My observation is that we can no more know what is “essential” to God than what is “accidental”, and thus cannot tell if a correlation of external effects is proof of cause or just coincidence.
    In other words, as I understand it, we can’t know what is essential to a proof of God’s existence unless He himself tells us who He is.
    After all, knowledge of God and of Christ is self-revelatory in nature, not only because He chose to reveal Himself to us, but also because in our fallen state we cannot know God without intervention on His part.
    I hope this makes sense!

  14. In a state of superdense matter which then exploded flinging matter outward to form the universe.

    The rapid transformation of potential to kinetic energy would have resulted in a high entropy lifeless universe. We see a relatively low entropy universe.

    Although I’m not sure how gravity works when a area of superdense matter (which is the entire universe) has no space around it to distort. I’m dubious about the ability of any amount of energy to displace such a massive object.

    Moreover if that were the case we would see an evenly distributed expanding dust cloud. Well we wouldn’t see it because we wouldn’t exist. The universe is lumpy, not even, even on the grand scale which is a source of frustration to many scientists who believe in cosmological evolution.

    Even cosmological evolutionists don’t posit all types of matter coming out of the “big poof” (as in the cloud of smoke a magician uses to hide their tricks). Rather they believe that hydrogen condensed into pure hydrogen/helium stars which went super-nova scattering the heavier elements for later use by stars like our own. Unfortunately no evidence exists for this type of star.

    The “big poof” is much like God’s direct creation inasmuch as it’s an article of faith. The difference is that God’s direct creation is consistent with the universe we see, whilst the claims of the “big poof” are inconsistent with the universe that is.

    Finally of course, a block of superdense matter exists but does not itself explain its own existence. Ex nihilo, nihilo est if my bastardized Latin can convey the point across.

  15. Let us remember that the question was “Can it be demonstrated that God exists.” I say “No, it is a matter of faith as much as the position that there is no God.” I have heard many lame-brained attempts to use science to prove the existence of God (Note that I am not referencing anyone here — only what I have heard). Usually those who attempt this are not qualified to speak regarding scientific matters even though they like to pretend that they have such ability. Why don’t we leave science to the scientists and theology to the theologians? The average pew-sitter doesn’t qualify as either though that doesn’t mean that they can’t understand their faith just as the average man-on-the-street can have some appreciation of science without being fully knowledgeable in the field.

  16. I have heard many lame-brained attempts to use science to prove the existence of God

    Moreover I did not claim it “proved” the existence of God. What I was saying was that based on the evidence in front of us it is reasonable to assume there is a creator.

    Outside the field of pure mathematics there is no such thing as “proof” (and no I can’t prove that). However it is possible to provide inferences such as “nature displays features characteristic of designed structures, therefore these natural structures may have been designed” that can support a theistic position.

    To strengthen those inferences it is also necessary to show that alternate positions are inferior in their explanatory power. For example “mutation and natural selection have only demonstrated the ability to produce phenotypic changes requiring three point mutations, intelligent causation is a more reasonable explanation of features that would require more than this”.

    Science is merely a tool, a process of observation, hypotheses forming, and testing used to form models that can explain how things happen (N.B. those models may not be “true” but they are intended to be useful). It’s certainly no sacred cow that is beyond reproach.

  17. And why should the orderliness or apparent design of creation be a sign of divine action? We do not have the essential postulates to begin such a proof unless God himself revealed to us in His wisdom what His attributes are. The Bibile tells us right from wrong, but it also tells us God from what He created.
    Proof of and knowledge of God is self-revelatory in nature; let us cast off the hubris of trying to “prove” He exists within our own human abilities.
    Otherwise, we would not need faith, it would be (intellectual) works.
    ” . . . it was nonsense to the Greeks . . .”

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