Question: Can God create a rock so big, that even he cannot lift it?
Premise: If God is omnipotent, that means he can do anything.
Answer 1) God can't create a rock that is so big that He can't lift it.
Implication 1a) Then God can't "do" everything.
Answer 2) God can create a rock so big that He can't lift it.
Implication 2a) Then He's not omnipotent
Conclusion: God's omnipotence is self-contradictory, thus making God's existence impossible. Therefore, God does not exist.
Initially this might sound impressive, but it is actually a house of cards. Let's set aside the Clark/Van Til controversy, on whether or not God is bound by the laws of logic, as that discussion isn't even necessary here. Supposedly, the unbeliever here has found incoherence in the attributes of God, namely, in the very definition of "omnipotence." However, what has happened here is that they have simply stacked the deck by redefining omnipotence in their premise. If you look back at the premise, omnipotence is being vaguely defined as the belief that "God can do anything." However, is that really what the definition of omnipotence is?
The answer is no. Omni, literally means "all" or "universal," whereas potent means "power," "influence," or "effect." Remember in science class when we learned about "potential energy?" Similar concept. So omnipotence literally means that God has all, or unlimited power, or force. So by definition, if God is omnipotent, than no object could ever be beyond His power. This is logically consistent, and perfectly understandable. However, by redefining "omnipotence" as the ability to "do anything," and not as referring specifically to force/power, the unbeliever gives himself wiggle room for a bait-and-switch. What do I mean? Well lets look back at the question, with a clearer definition of omnipotence.
Premise: If God has unlimited power, then nothing he creates can be beyond his power.
Answer: God could never create a rock beyond his power.
Conclusion: Uhm, what's the point again?
See, the skeptic is trying to claim that God's omnipotence leads to a contradiction. But all they have done is a bait-and-switch by including a contradiction in the demands of omnipotence, and then they cover it up with a pliable definition ("he can do anything"). In other words, they are demanding that God show he has unlimited power, by having limited power (being able to to create a rock so big, etc...). This makes no sense, and is definitely not a standard set by the divine attribute of omnipotence. So instead of setting forth the incoherent premise "if God has unlimited power, he must have limited power," they instead frame it as "if God has unlimited power, he must be able to do anything." That latter phrase, "he must be able to do anything," is left undefined and can pertain to all sorts of things beyond power/potency. In this case, it's a cover for them demanding He be able do something which contradicts the very concept of having unlimited power! It makes no sense. God's attributes do not lead to contradictions, but to clarity. The unbeliever includes a hidden contradiction in their premise, in order to make the conclusions appear contradictory.
If unbelievers really want to be wowed by what God is able to do, they should examine the two natures of Christ. That doctrine certainly transcends our created understanding of logic without contradicting it. We would expect that if the eternal, transcendent God of Scripture has condescended to man, he would introduce concepts that would stretch our finite apprehensions. The doctrine of the incarnation does just that. The second person of the Trinity took a human nature onto his divine nature, and united the two, "inconfusedly, unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved," as the Chalcedonian Creed tells us. Find the largest rock that man is able to lift, and Jesus in His human nature could go no further. In fact, not only was Jesus limited in His human nature, but He Himself was also crushed by a much heavier weight. The weight of God's wrath. And He did it to redeem cosmic rebels, who make up silly syllogisms in order to escape their responsibility and guilt.
"Yet it pleased the LORD to bruise him; he has put him to grief: when you shall make his soul an offering for sin, he shall see his offspring, he shall prolong his days, and the will of the LORD shall prosper in his hand." (Is 53:10)
