Is it really possible to demonstrate, in reason or logic, that God exists?
Aquinas cites three objections: 1. God is supposed to be approached through Faith, not to be sought after by the unassisted human mind – this is normally the case for religions that have an incomprehensible God.
2. God’s Essence is incomprehensible. So, how could I even begin to prove that He exists? Even if I came upon God’s presence, or tokens of this presence, how could I comprehend those? Or, how could I know what to compare my experiences with, so as to prove that God exists?
3. God is infinite and the human mind is finite and limited. There is a vast disproportion here. If I were to “prove” God through His effects in the world, how could I possibly do this? Shouldn’t the effects of an infinite God also be infinite themselves? If so, how could my finite mind grasp, comprehend, or even recognize and describe such effects of a infinite God?
As he always likes to do, Aquinas answers all the objections. 1. Reply to objection 1: In Christianity, faith itself presupposes natural knowledge. For instance, faith in salvation presupposes understanding of human nature – and human nature’s sinful limitations and passions. So, faith and natural knowledge are not mutually exclusive.
2. Reply to objection 2: Although God’s essence is incomprehensible for the limited human mind, it is still possible to define God through the various attributes that we know are to be attributed to God. For instance, we can be told by holy books, etc., that there are certain attributes, which define God for us.
3. Reply to objection 3: Although it is indeed impossible to get a perfect knowledge of a disproportionately great Cause from its effects, it is still possible to infer that some Cause exists based on its effects. So, even if we become aware of a tiny fraction of the effects of a divine cause, we can infer that a divine cause EXISTS, even though we cannot hope to get to know this divine cause in its essence.
So, Aquinas concludes that it is possible to demonstrate God’s existence in logical ways, and he proceeds to offer his FIVE WAYS – which you can find in the assigned text.
Recall your reading, by J.J.C. Smart, on philosophy as the "elimination of nonsense." Some philosophers think that all statements about God - as God is perceived by non-naturalistic, transcendental religions - are nonsensical arguments. Here is what they have in mind: Can we say under what conditions we could check whether the propostion 'God exists' is true? Could we check under what conditions the proposition 'God exists' is FALSE? [Remember, it is the same thing - if you know what it takes for something not to be true, then you must know what it takes for it to be true.]
What about God? What WOULD it take to find out if 'God exists' is true or false? [If we cannot figure this out, then, the sentence might be nonsensical - of course, even in that case, one can still believe in God, but one would admit that language does not allow us to speak of God or prove that God exists. For instance, one might claim a mystical view or intution of God and God's truths, but how would this person translate the mystical sight into exeriences that are out there for all to grasp?] So, what would it take to affirm or falsify the assertion that God exists?
Would any concrete empirical sign [any sign from experience] do it? But, note that any such sign would NOT be confirming the concept of God which Judaism, Christianity, and Islam assert - a God who TRANSCENDS nature and experience.
What about NATURE - nature's orderly design and regularities? There are objections to this from contemporary biology, of course; but, even beyond that, there is another problem too: If it is NATURE we are talking about, we can only prove something about nature - NOT about a supernatural or transcendent entity. For instance, even if you infer that there is an ARCHITECT who designed the plan of nature, this architect is still a natural mind - INSOFAR as your natural mind comprehends nature; if there are things about nature you are not able to understand, then how would you know that such things are also orderly, purposeful, 'designed?'
It seems that we are stuck with only the other kind of 'proof' - proof not from experience but from logical reflection on the definition of God. This is the kind of proof Anselm tried to provide. But what kind of 'proof' this is? By unfolding the definition of God-as-the-greatest-being, we cannot go wrong - in the same way that we cannot wrong by repeating the definition of a triangle - we then know what a triangle is. But how could we PROVE that a triangle EXISTS by repeating its definition? Are we not PRESUPPOSING that a triangle is what it is when we define it? Where is any NEW information about triangles when we repeat what we already know - the definition of a triangle? Isn't the same problem confronting those, like Anselm, who try to prove that God exists based on the definition of 'God'?