2
The Logical Problem

Establishing the first moment of the "contemporary" in any domain inevitably involves a certain amount of arbitrariness. With this said, it isn't completely arbitrary to treat the publication, in 1955, of J. L. Mackie's essay "Evil and Omnipotence" as the initial salvo in the contemporary debate over the problem of evil.

Obviously, as I have already emphasized, evil has been taken to be a problem for theistic commitment from philosophical time immemorial. However, Mackie's argument introduced a distinctly argumentative structure into the debate. That is, Mackie formulated his complaint, as we will see, quite explicitly as an argument against the claim that God exists. By contrast, while the history of the discussion certainly brought evil to bear on the rationality of religious belief, this aspect of the problem was frequently enmeshed with a related but distinct problem of explanation. As a case in point, Leibniz, in his Theodicy, often treats the problem principally as having to do with how theism can account for the existence of evil rather than as a worry that God does not exist. The same, I think, can be said even for Hume's treatment of the issue in his Dialogues Concerning Natural Religion.1 Prior to Mackie's challenging argument, the existence of evil was taken not so much as a consideration favoring atheism but more commonly as the source of an explanatory gap that theism should try either to fill or explain away. Conceived of in this way, the problem is essentially internal to theism, and the failure of theism to address it satisfactorily might have been just one more place at which theologians and philosophers of religion were called upon to continue the ongoing work of rendering the theistic worldview acceptably coherent to its adherents. Like the doctrine of the Trinity or the package of issues regarding divine foreknowledge, the problem of evil might only have structured a theological project rather than a deep challenge to the existence of God. Mackie's argument and its profound influence decisively changed all of this - and made it impossible for philosophers of religion, in particular, to treat the existence of evil merely as an explanatory problem internal to the religious point of view. In doing this, Mackie's argument set the agenda for the philosophical discussion of the problem of evil that has ensued in the decades since.

2.1    Mackie's Argument

The initial grip and the enduring power of Mackie's argument are to be found in both its boldness and its clarity. With respect to its elegant boldness, Mackie positions his argument as a more forceful alternative to the traditional atheistic strategy of attack on the standard theistic arguments. The problem with the traditional strategy, he notes, is that the theist can, in principle, accept the full range of complaints about the various arguments for the existence of God without being rationally required to give up theistic belief. The argument he offers, however, can, he thinks, cut deeper than the traditional strategy.

Mackie begins thusly:

The traditional arguments for the existence of God have been fairly thoroughly criticized by philosophers. But the theologian can, if he wishes, accept this criticism. He can admit that no rational proof of God's existence is possible. And he can still retain all that is essential to his position, by holding that God is known in some other, non-rational way. I think, however, that a more telling criticism can be made by way of the traditional problem of evil. Here it can be shown, not that religious beliefs lack rational support, but that they are positively irrational, that the several parts of the essential theological doctrines are inconsistent with one another, so that the theologian can maintain his position as a whole only by a much more extreme rejection of reason than in the former case. He must now be prepared to believe, not merely what cannot be proved, but what can be disproved from other beliefs that he also holds. (1955, 25)

The boldness here shouldn't be undersold. Mackie intends to produce an argument that will render theistic belief "positively irrational" by revealing its essential inconsistency. If he succeeds, then theistic belief will be worse than belief in the existence of Bigfoot or the Loch Ness Monster: though the existence of these controversial creatures is woefully unsupported by compelling evidence, at least there is no conceptual incoherence built into the idea of either. Theistic belief will, rather, be like belief in the existence of round squares or in the existence of two things equal to a third thing that are not equal to each other. We don't reject the existence of these items on evidential grounds, but because to do otherwise is to accept contradictions. On Mackie's reasoning, then, the thesis that God exists doesn't so much as rise to the level of being a proper object of evidential concern. The Chupacabra should have it so bad.2

But boldness is not the only virtue of Mackie's argument. The argument is also admirably clear. What Mackie emphasizes is that the problem of evil, as he is conceiving of it, is a logical one (and thus the title customarily given to his argument).3 It is a problem with the logical relations among the things that the theist claims to believe.

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. But at the same time all three are essential parts of most theological positions: the theologian, it seems, at once must adhere and cannot consistently adhere to all three. (1955, 25)

The effort to make this apparent contradiction evident is the soul of the logical problem of evil and of Mackie's argument. The intuitive idea would seem to follow upon the questions we earlier saw raised by Epicurus. If God exists and is omnipotent, then God is able to create a world without evil. If God exists and is wholly good, then God wants to create a world without evil. Thus, the fact of evil in the world is logically inconsistent with the existence of an omnipotent and wholly good God.4

Mackie recognizes, however, that this intuitive idea needs fleshing out. Specifically, he recognizes that the existence, omnipotence, and omnibenevolence of God do not strictly entail that there is no evil. In other words, Mackie has a little work to do to reveal that there is a formal contradiction in the set of propositions that the theist accepts. To do this work, Mackie proposes (or invokes) two additional propositions: one regarding goodness and one regarding power. The goodness proposition is that a good thing always eliminates evil as far as it can. The power proposition is that there are no limits to what an omnipotent thing can do. Taken together, now, Mackie believes that a contradiction is in the offing. One crisp way of seeing the supposed contradiction is by formulating Mackie's argument as a reductio ad absurdum. Thus, Mackie is convinced that the following five propositions

1. (1´) God exists.
2. (2´) God is omnipotent.
3. (3´) There are no limits to what an omnipotent being can do.
4. (4´) God is omnibenevolent.
5. (5´) A good being eliminates evil as far as it can.

together entail

1. (6´) Evil does not exist.

But (6´) is the absurdum; it is obviously false - and, indeed, the theist herself will insist that this is so. Since (6´) is false, claims (1´)-(5´) cannot all be true together (since they entail an obvious falsehood). That is, this set of claims must be logically inconsistent. Insofar as the theist accepts all six claims, she appears to be accepting a contradiction. This is surely the most damning complaint a philosopher can muster against a view.

After attempting to make explicit the logical inconsistency in the set of propositions the theist endorses, Mackie spends the lion's share of his famous article considering and criticizing anticipated responses to his argument, a number of which have been influential in the history of philosophical reflection on the problem of evil. In fact, we will have occasion to reflect somewhat more deeply and in particular upon Mackie's response to the invocation of human free will in response to his argument. For now, though, we should take note of the fact that Mackie appears to be aware that his extra premises - (3´) and (5´) - are controversial. He recognizes, particularly, that the theistic tradition has been willing to impose, at the very least, logical constraints on the power of an omnipotent being, contra (3´). Mackie is prepared to treat this concession (as he seems to be thinking of it) as something of an embarrassment to theism. He notes that, "a few have been prepared to deny God's omnipotence, and rather more have been prepared to keep the term 'omnipotence' but severely to restrict its meaning, recording quite a number of things that an omnipotent being cannot do" (1955, 26). There is a nice bit of rhetorical implicature here that the natural or commonsensical theistic view of omnipotence is being contorted into this untoward shape by the ad hoc effort to address...