Can God create a rock so heavy that he cannot lift it?

This question is often used as evidence against the existence of God. The argument goes like this:

• If God can create a rock too heavy to lift, then he is not omnipotent because he cannot lift a certain rock.
• If God cannot create a rock too heavy to lift, then he is not omnipotent because he is unable to create a certain rock.

Superficially, this seems like a pretty damning argument against the existence of God, who is invariably described as omnipotent - nothing is beyond his power.

Nothing, that is, except the logically impossible. And I think that is where this argument falls down. It is asking whether or not God can do the logically impossible, which is a totally meaningless question, and therefore of no use one way or another.

For example, consider these similar questions :

• Can God make a vehicle which moves so fast that he cannot catch it?
• Can God draw a picture so small that he cannot see it?
• Can God bake a cake so large that he cannot eat it?
• Can God make a star so bright that he cannot look at it?

These could easily be used in place of the Heavy Rock question, but are unfortunately just as meaningless. Apart from the basic problem of where God would stand in order to lift the rock, or what the rock would itself stand on, the question amounts to "Can God do something that God cannot do?" or "Can God find the limits of his unlimited abilities?" which are logically incoherent. This is called a fallacy of Contradictory Premises, as one statement contradicts the other ("God's abilities are unlimited" vs. "God's abilities are limited").

You may as well ask

• Can God make a circular triangle?
• Can God create a colour that he cannot smell?
• Can God formulate a proof of his own non-existence?
• Can God outrun himself?
• Can God cauliflower?

These questions can be asked, but just because a question can be asked does not mean that it has any value, or is deserving of any sort of response.

What flavour is Thursday?

Why do bananas enjoy driving tractors?

You can string a bunch of words together to make a syntactically valid question, but if the question is meaningless then what use is it? That, I think, is the case with the Heavy Rock dilemma - it is based on a logical impossibility ("Can God do what God cannot do?") and just becomes so much pointless word-play.

Even slightly more sophisticated examples like
Can God create a being equal to himself?
fall into the same trap. This one sounds good at first, but the problem here is that God is, allegedly, un-created. He has always existed. How could God create a being that has not been created? It appears valid at first, but God not being able to do something that cannot be done and is logically impossible is hardly evidence against God.

Another way of looking at it is like this:

1. Can God do the impossible?
   Yes (if you are referring to things that are simply impossible for non-omnipotent beings like us, like holding a picnic inside the sun).
2. Can God do the possible?
   Of course (although beings like us may not be able to).
3. Can God do the logically impossible?
   No, because they are not "there" to be done. Circular triangles and so on. The question itself is unlikely to make much sense.

The Heavy Rock question may work as an attention-getter, and waken the theist to the fact that people ask awkward questions about their deity. They may believe "With God, all things are possible", but you may make them understand that this does not include the logically impossible, and simply saying "God can do anything he wants to" doesn't cut the mustard. However, as a convincing proof against a God it fails pretty quickly. Atheists should realise the problems with it before relying on it in an argument, otherwise they are likely to be shot down in flames by any reasonably savvy opponent. There are far stronger and more coherent logical arguments against the existence of Gods (free will vs. omniscience, gratuitous evil vs. omnibenevolence, and so on).

Those who enter into "battle" with a Christian, wielding the Rock argument as their only weapon, are going to about as successful as the naive young evangelist who thinks all he need do is say "Jesus loves you", and atheists will convert and rush to the nearest church like lemmings.

It's probably unusual for an atheist to criticise a commonly-used argument against God, but I really don't think the Rock problem is a valuable addition to our arsenal except maybe as a counter to the "God can do whatever the heck he likes" assertion.

If an omnipotent God exists, then it can do anything, as long as that action is logically possible.

© Copyright Adrian Barnett 1999

[ Note: One possible objection to this line of reasoning is "God is not bound by the rules of logic, as he created logic, therefore he can do the logically impossible as they are only logically impossible from our point of view". If this were the case, however, it would seem to be impossible for anyone to ever know anything about God at all, or attempt to understand him using reason and logic. It would make no sense for any theist to attempt to describe the character of their god as, for instance "good, merciful and loving" because there would be no reason to think that this could be true. You could not say, for example, that God is good because he has healed a person, as an illogical God could just as easily have done it for any reason at all other than goodness - by our standards it might appear to be "good", but that would be no reason to assume that it was good as far as God was concerned. ]