God Cannot Do Everything
While in college, my wife once had a professor who posed what he apparently thought was a debilitating problem for Christianity: “If God can do everything, can He make a rock so big that He can’t pick it up?” Christians affirm something very similar to the first part of the sentence; the Bible teaches and we believe that God is omnipotent, which means that God has the power to do anything He wants. God’s power is not curtailed by anything exterior to Himself; if God chooses to do something, no one and nothing exterior to Himself can keep Him from accomplishing His purpose. Since God is omnipotent, can He make as stone so large that He cannot pick it up?
The answer to this question is pretty simple: No, God cannot make a rock so big that He can’t pick it up. You may think that the negative answer is strange because it says there is something that God could not do. Initially, this seems to challenge the doctrine of omnipotence, which the Bible clearly teaches; consider, for example, Genesis 18. In Genesis 18, God tells Sarah, who had struggled with infertility, that she will have a baby. Sarah is incredulous and laughs at God who then responds with a rhetorical question: “Is anything too hard for the Lord?” In context, the answer is clearly no. Similarly, in the Old Testament book of Job, Job, after hearing directly from God, says to God, “I know that you can do all things; no purpose of yours can be thwarted.”
While the Bible does teach omnipotence, omnipotence is not what most people think it is. The reason that people think that the question about the rock—which is really a juvenile objection—is a problem for Christianity stems from an incorrect understanding of divine omnipotence. Christians believe that God can do just about anything—even things we would consider naturally impossible, such as making the elderly Sarah have a baby, giving the blind sight, and raising people from the dead. Christians do not believe, however, that God can do literally anything. Consider, for example, James 1.13: “God cannot be tempted, nor does he tempt anyone.” Or, consider Numbers 23.19: “God is not humans, that he should lie, not a human being, that he should change his mind.” Further, since God is omniscient, it seems pretty clear God cannot learn anything. What’s more, since God has the quality of aseity, He cannot cease to exist. To end what could be a very long list, since God is omnipresent, God can never leave a place, at least not in an absolute sense. My point should be clear: There are a lot of things that God, due to His nature, cannot do.
Here’s what Christians actually mean by omnipotence: We believe that God can do any action provided that the action is (1) logically possible and (2) consistent with His nature. Thus understood, God’s omnipotence does not mean that He can make a rock so big that He can’t pick it up; such an idea is logically impossible and thus violates (1). Not only that, God cannot make a 3-sided square, a round triangle, or a married bachelor. God cannot make 2+2=5 any more than He can make 8 be a prime number. God cannot make the two sentences, “Jones is mowing his lawn” and “Jones is not mowing his lawn,” true at the same time and in the same sense. All of these sentences convey no meaning; they’re pure non-sense and semantically void.
At this point you should see another objection: If God is subservient to logic, then how can He be God. It would seem that I’ve made logic out to be God, which is idolatrous. However, consider this: Why can’t God be tempted or change His mind, as James and Numbers tell us? The reason is that these things violate His nature. Since God is holy by nature, temptation is not even a factor for Him, nor can He encourage others to do evil. Similarly, since God is immutable and omniscient, it’s contrary to His nature to change His mind. The reason that God can’t be tempted and can’t change His mind is not due to something exterior to Himself; these limits are internal to God. God cannot and does not violate His own nature; therefore, He cannot do anything contrary to His own nature, such as lie or change His mind.
Now consider logic: Where did we get logic? Who says that 2+2=5 is always wrong? Who says that a triangle can’t be round or a square can’t have 3 sides? Why can’t the sentences, “Jones is mowing his lawn” and “Jones is not mowing his lawn” be true at the same time and in the same sense? Who established these rules by which we must abide? Logic, just like morality, comes from God. Consider one example: Human beings are able to use logic and measurements to predict that there will be a total solar eclipse on June 14, 2151. Think about that: Barring any massive advancements in medicine, every person on earth right now will be dead when that eclipse happens. Nevertheless, we know that this eclipse will take place; NASA even has a map of the eclipse’s path over Canada! Where did this order come from? The Psalmist says: “The heavens declare the glory of God; the skies proclaim the work of his hands.” Paul says: “God’s invisible qualities…have been clearly seen” in creation. From the logic of the created world, we can know that God is a supremely logical being.
As a side note, we should be very glad that God is logical. Were He not logical, God could command us to do evil things and command us not to do evil things without violating His nature. Were God not logical, He could be both good and bad at the same time and in the same sense. We ought to be thankful that our God is not like that!
Why can’t God make a rock so big that He can’t pick it up? Because that is logically impossible. Since God is a logical being, we know that He does not do anything illogical; for an illogical action, much like lying and changing His mind, would be contrary to His nature, and God never violates His nature.
Notes & Sources
 Genesis 18.14, all Scripture quotations are NIV.
 Job 42.2
 James 1.13
 Numbers. 23.19
 “Total Solar Eclipse of 2151 June 14,” NASA, accessed October 9, 2017, https://eclipse.gsfc.nasa.gov/SEsearch/SEsearchmap.php?Ecl=21510614.
 Psalm 19.1
 Romans 1.20