“In its simplest form the problem is this: God is omnipotent; God is wholly good; and yet evil exists. There seems to be some contradiction between these three propositions, so that if any two of them were true the third would be false. (…) However, the contradiction does not arise immediately; to show it we need some additional premises (…) These additional principles are that good is opposed to evil, in such a way that a good thing always eliminates evil as far as it can, and that there are no limits to what an omnipotent thing can do. From these it follows that a good omnipotent thing eliminates evil completely, and then the propositions that a good omnipotent thing exists, and that evil exists, are incompatible.”

J.L. Mackie, “Evil and Omnipotence,” 200-201

J.L. Mackie’s 1955 article “Evil and Omnipotence” is a well-known piece of twentieth century philosophy of religion.[1] I will not be discussing the entire article here, I rather want to use it as a starting point for some reflections on the standard logical problem of evil, on which, roughly, the existence of a wholly good and omnipotent God is incompatible with the existence of any evil. If the existence of such a God is indeed incompatible with the existence of any evil, then there is a serious problem for theists who believe in an omnipotent and wholly good God, since some evil seems to exist. As we can see above, Mackie sought to show the incompatibility of the existence of such a God and the existence of evil and in the process he made use of two principles: (1) “good is opposed to evil, in such a way that a good thing always elmininates evil as far as it can” and (2) “there are no limits to what an omnipotent thing can do”. If these principles are true, then, indeed, the existence of evil is incompatible with the existence of an omnipotent and wholly good God. Moreover, a strong argument could then be constructed against the existence of such a God, something, for instance, along the following lines:

1. If any evil exists, no wholly good and omnipotent God exists.
2. Some evil exists.
3. Therefore, no wholly good and omnipotent God exists.

So, are Mackie’s principles true? Both initially seem somewhat plausible. But we may nevertheless have some questions about them. First, what does it mean exactly that a good thing always eliminates evil as far as it can? Does it mean that a good being always makes the total amount of evil as small as possible, even if that involves doing evil? Suppose, for instance, that a good person could prevent a serial killer from killing tens of people and could thus make the total amount of evil smaller than it otherwise would be, but could only do so by killing the serial killer, would that person then kill him? Or would a good person, by definition, be unable to do something evil, even if that would minimize the total amount of evil?

When it comes to the second principle we might wonder whether it is really true that there are no limits to what an omnipotent thing can do. Consider the following argument:

1. If there is something an omnipotent thing cannot do, then there are limits to what an omnipotent thing can do.
2. An omnipotent thing cannot not be omnipotent while it is omnipotent.
3. If (2), then there is something an omnipotent thing cannot do.
4. Therefore, there are limits to what an omnipotent thing can do.

Now, one may object that an omnipotent being by definition is such that there are no limits to what it can do. Well, if that is true, then maybe the theist should concede that there is no omnipotent God and instead insist that there is a wholly good God whose power is perfect. Perfect power seemingly does not require being able to the impossible. If it were the case that one can be perfectly powerful and unable to the impossible, then there seems to be a way in which such a God and some evil could co-exist. After all, if the evil were impossible for this God to eliminate, then the existence of this evil would be compatible with the existence of such a God. But surely, one might say, there is no (possible) evil that is impossible for such a God to eliminate?

Well, maybe things are not quite so straightforward. Consider the following scenario: A wholly good God exists who has perfect power, but is not able to do the impossible (we’ll call this being God₂). This God is faced with the choice of creating or not creating contigent beings and is free to choose either option. However, God₂ cannot actualize any old world with contigent beings. Because God₂ is wholly good, God₂ cannot, for instance, actualize worlds with on balance more evil than goodness and cannot actualize a certain world if God₂ could actualize one with more goodness (in cases where the total amount of evil is equal). But many contigent goods are such that they require the (prior) existence of some evil to exist. Now, suppose that all worlds with greatest amount of goodness include such contigent goods. It follows that if God₂ creates a world with contigent beings, God₂ cannot but create one with some evil. The evils in question would not exist necessarily, since God₂ could decide not to create any contigent beings. Moreover, the evils in the maximally good worlds need not be the same. Lastly, it need not be the case that evils exist at every moment of the history of these worlds. If this scenario is (logically) possible, then it seems the existence of God₂ is compatible with the existence of (some) evil.

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[1] J.L. Mackie, “Evil and Omnipotence,” Mind 64, no. 254 (1955): 200-212.