It is of utmost importance that we keep the proper purpose of this essay in mind. It is an answer to Mackie's claim that the problem of evil is a logical problem. Mackie states "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 doctrine are inconsistent with one another . . ."
The problem of evil has many dimensions. Plantinga's essay "The Free Will Defense" addresses the logical problem. As Plantinga notes, "Neither a free will defense nor a free will theodicy is not designed to be of much help or comfort from such a storm in the soul [like the experience of Job] . . . . Neither is to be thought of first of all as a means of pastoral counseling. Probably neither will enable someone to find peace with himself and with God in the face of the evil the world contains. But then, of course, neither is intended for that purpose." (p. 266)
Mackie asserts that Set A is contradictory. But in what way? It is not explicitly contradictory. Neither, is it formally contradictory. According to Plantinga, Mackie must believe that set A is implicitly contradictory.
(To make A formally contradictory, Mackie needs to add some aditional propositions which are necessarily true, given A.) Mackie suggests the following two propositions:
(19) A good thing always eliminates evil as far as it can.
(20) There are no limits to what an omnipotent being can do.
Are (19) and (20) necessarily true, given A? Plantinga thinks that it is perhaps plausible to suppose that (20) is necessarily true so long as one adds a qualification--there are no nonlogical limits to what an omnipotent being can do.
(19) is not necessarily true. At the very least, (19) needs to become (19a).
(19a) Every good thing always eliminates every evil that it knows about and can eliminate.
Assuming that set A includes the notion that God is omniscient as well as omnipotent (most theists will concede this point), is this new set {(1), (2), (3), (19a), and (20)} contradictory? Perhaps. But is (19a) necessarily true? Plantinga says "No." (19b) is a more nuanced proposition.
(19b) A good being eliminates every evil E that it knows about and that it can eliminate without either bringing about a greater evil or eliminating a good state of affairs that outweighs E.
[Hereafter Plantinga will use the phrase "properly eliminate" for "eliminate without either bringing about a greater evil or eliminating a good state of affairs that outweighs E." ]
Is (19b) necessarily true? No.
Plantinga concedes the necessary truthfulness of (19c):
(19c) An omnipotent and omniscient good being eliminates every evil that it can properly eliminate.
So now we have the new set (A'). It contains the following propositions:
Is this set formally contradictory? Not yet. For it to be formally contradictory, then from any five propositions, we must be able to deduce the denial of the other sixth proposition. We must also add (21):
Plantinga concedes that (A') plus (21) is formally contradictory. But is (21) necessarily true? Plantinga denies that (21) is true. Some states of affairs (for example, G and E) cannot be "properly eliminated" by definition. Plantinga notes that some might find this response to be an unpersuasive, "tricky and irrelevant." There are, however, other examples, but more to the point, Mackie's charge is that the original set A, when subjected to logical examination, is obviously incoherent. If by the rules of logic, (21) is not necessarily true, then the new set (A') plus (21) has not yet been shown to be formally contradictory.
Plantinga suggests that perhaps there are other propositions, which when placed in conjunction with set (A') might yield a formally contradictory set. Plantinga continues, "And our discussion thus far shows at the very least that it is no easy matter to find necessarily true propositions that yield a formally contradictory set when added to set A. One wonders, therefore, why the many atheologians who confidently assert that this set is contradictory make no attempt whatever to show that is." (112-13)
(22) God creates a world containing evil and has a good reason for doing so.
In what follows in the remainder of the essay, Plantinga wants to defend the following claims: since God desires for God's created beings that they be significantly free, then it is not possible that God could not have created a universe containing moral good without creating one that also contained moral evil. If this claim is true, then it is possible that (22) is true--which means that God has a good reason for creating a world containing evil.
Plantinga's preliminary statement of the Free Will Defense is:
A world containing creatures who are significantly free (and freely perform more good than evil actions) is more valuable, all else being equal, than a world containing no free creatures.
[For Plantinga, an action is morally significant for a given person is if would be wrong for that person to refrain from the action or vice versa. To be significantly free means that a given person is free with respect to morally significant action. Freedom is not to be confused with unpredictability.]
Bearing in mind that Plantinga is concerned to articulate a defense not a theodicy, he wants to assert "that is it possible that God could not have created a universe containing moral good (or as much moral good as this world contains) without creating one that also contained moral evil." (p. 268) Remember, Mackie asserts that the set is not possibly consistent; Plantinga is not concerned to show that it IS consistent, only to show one way in which it MIGHT be consistent."
The key here is Plantinga's claim that it is possible that God could not have actualized just any possible world God pleased. (A "possible world" is a way things could have been. A possible world is a state of affairs. God does not, strictly speaking, create any possible worlds or states of affairs. God actualizes states of affairs.)
See the illustration on pp. 274-76 to see how Plantinga demonstrates that the premise that God, if omnipotent, could actualize just any world God pleased is false.