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Last Updated on May 7, 2015, by eNotes Editorial. Word Count: 2968

Article abstract: Plantinga’s most famous contributions were to the philosophy of religion, although he also significantly influenced metaphysics, epistemology, and even philosophy of language.

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Early Life

Born while his father was pursuing a graduate degree in philosophy, Alvin Plantinga was heir to a long tradition of Dutch Calvinism. He attended Jamestown College (North Dakota), Calvin College, Harvard, and Calvin College (again) as an undergraduate, where he majored in philosophy and psychology and was particularly influenced by William Harry Jellema. In January, 1954, he entered the University of Michigan, where he took classes with William Alston, William K. Frankena, and Richard Cartwright. He then went to Yale, taking courses from Brand Blanshard, Paul Weiss, and Frederick Fitch and completing his doctorate in philosophy. He also taught at Wayne State University, Calvin College, and the University of Notre Dame, where he became the John A. O’Brien Professor of Philosophy.

Life’s Work

Best known for his philosophy of religion, Plantinga addresses the problem of how an omnipotent, omniscient God and evil could coexist. He uses the notion of possible worlds and possible persons as well as logical reasoning to argue for the existence of God.

Plantinga is enthusiastic about the philosophical usefulness of the notion of a possible world. Two standard ways of explaining this notion appeal to maximal propositions and maximal facts. A proposition is what is expressed by the standard use of a declarative sentence, namely an assertion of something. Thus what is expressed by “Two is twice one” is one proposition and what is expressed by “No U.S. president has been a Martian” is another proposition. Similarly, “two’s being twice one” is one fact and “no U.S. president’s having been a Martian” is another fact.

One proposition P entails another proposition Q if it is not logically possible that Q be false if P is true. Otherwise stated, P entails Q if and only if “P is true and Q is false” is self-contradictory. It is logically impossible that “Charles has always weighed less than two hundred pounds” be true and “Charles has always weighed less than three hundred pounds” be false. Thus the former proposition entails the latter.

Some propositions entail certain propositions and not others. “Two is twice one” entails “Two is not less than one” but it does not entail “The population of Ireland is not less than one.” “No U.S. president has been a Martian” entails “No U.S. president has been a Martian male” but it does not entail that “No U.S. president has been male.” However, if P is a maximal proposition, then for every proposition Q, either P entails Q or else P entails not Q. A true maximal proposition thus contains an incredible amount of information. In fact, if P is a true maximal proposition, it is also the true maximal proposition; there can be only one. Each maximal proposition describes a different possible world; self-contradictory propositions do not count as maximal propositions. A maximal proposition describes a total way that things might be. Further, if P is a maximal proposition, then it is what logicians call a logically contingent proposition; it is logically possible or non-self-contradictory that P be false. Thus each maximal proposition describes exactly one possible world, and to say “Maximal proposition P is true” is the same as to say “The possible world that maximal proposition P describes exists.”

One fact can include another; the fact of “Tom’s being tired and Tess’s being reflective” includes the fact of “Tom’s being tired.” One fact can preclude another; the fact of “Tom’s being tired” precludes “Tom’s not existing.” A run-of-the-mill fact includes some facts and precludes others. A maximal fact F has this feature: For any fact F*, F either includes F* or F precludes F*. If F is a maximal fact, then F either includes or precludes each of the following: “Maude’s being a millionaire,” “Hoover Dam’s being in Colorado,” “Berkeley’s notebook on notions being discovered by the tallest woman in Rome,” and “the starting quarterback of the Minnesota Vikings in 2001 being female.” A maximal fact is a possible world. There are possible facts, which are facts that might obtain but do not. For example, “there being unicorns,” “there being flying pigs,” “there being money-bearing trees” and the like might have obtained. Because they do not obtain—because there are no unicorns, flying pigs, or trees whose fruit is cash—they are merely possible facts. Every maximal fact—every possible world—is a possible fact. All maximal facts are merely possible save for one, namely the maximal fact that is actual, the actual world. Thus, according to Plantinga, a possible world is described by each maximal proposition; every maximal fact is a possible world. The true maximal proposition describes the actual world; the actual world is the maximal fact that obtains.

A necessarily true proposition is one that is true in all possible worlds. “Two is twice one” is true in all possible worlds, and Plantinga holds that “God exists” and “There are propositions that are necessarily true, or true in all possible worlds.” A necessarily false proposition or self-contradiction is true in no possible world and false in all possible worlds. “One is twice two,” for example, is false in all possible worlds. Logically contingent propositions—propositions that are neither necessary truths nor necessary falsehoods—are true in some possible worlds and false in other possible worlds. “There are unicorns,” “All U.S. presidents have been women,” “Many caves are occupied by bats,” and “In some cultures, weddings are arranged by the parents of the bride and groom” are true in some possible worlds and false in others.

There are also, in Plantinga’s view, possible caves, possible plants, possible wombats, and possible persons. A crucial point to remember is if X is actual then X is possible (nothing impossible can be actual) but if X is possible then X may or may not be actual. If it is actual that a particular armadillo weighs exactly seven pounds for all of its adult life, then it is obviously possible that it have this weight for all of its adult life. However, just because it is possible that an armadillo weigh exactly seven pounds for all of its adult life it does not follow that one actually does have that weight for all of its adult life. To talk of merely possible caves, plants, wombats, and persons is to talk of ways things might have been but are not regarding caves, plants, wombats, and persons. If certain descriptions that might have been true had actually been true, then there would be caves, plants, wombats, and persons that there are not. A merely possible person is a description such that, had God made the description true, God would have made a person.

The notion of merely possible persons versus that of actual persons plays an important role in Plantinga’s discussion of whether the existence of evil provides reason to think that there is no God. Some philosophers have held that “There is evil” and “God, who is omnipotent, omniscient, and morally perfect, exists” are logically incompatible claims; if one is true, the other is false. Plantinga argues that this cannot be correct. He uses the following consistency strategy: If a set of three propositions A, B, and C form a logically consistent set, then any pair selected from that triad of propositions will be logically consistent. Thus, if we begin with A: “Australia is not New Zealand,” B: “Puppies are cute,” and C: “Baseballs are not typically made of cabbage,” and note that (1) none of A-C taken singly is self-contradictory, and (2) A-C taken collectively is logically consistent, then it follows that (3) any pair of propositions taken from A-C will be logically consistent. This is independent of the truth of A-C: It does not matter if all are true, all are false; or some are true and some are false, as long as (1) and (2) are the case, then (3) follows.

Consider, then, Plantinga suggests, these examples: A: “God exists,” B: “God has a morally sufficient reason for allowing any evil that God does allow,” and C: “There is evil.” It is not too hard to see that A-C satisfy (1) and (2). None of A-C seems, by itself, self-contradictory. The group A-C seems to be not self-contradictory. However, if A-C satisfy (1) and (2), it follows that they satisfy (3). Any pair of propositions taken from A-C are logically compatible. “God exists” and “There is evil” are included in A-C. So “God exists” and “There is evil” are logically compatible.

This line of reasoning leads to a further objection of the following sort. It is logically possible that there have been persons that there are not. It is possible that Abe, who has one brother, had seven. It is possible that there not have been the persons that there are; Abe and his brother might never have existed. The core of the objection concerns a possibility that will hold if God exists. The condition is this: If God is omnipotent, omniscient, and morally perfect and creates the world, then God will create only persons who are morally perfect.

The reasoning behind this condition is as follows: Plantinga holds that in order for people to be moral agents, they must be free agents. People are free relative to an action at a given time if, under the conditions that actually prevail at that time, they can perform that action or can refrain from performing it. Neither performing it nor refraining is determined by the past. Suppose this is so, and consider some merely possible person—some description such that, if God makes the description true of something, God has made a person. Let this description include the element “actually makes morally relevant choices, makes them freely, and always makes them rightly.” Let any possible person in whose description this element occurs be a possible moral saint. If every actual person is a moral saint, then there will be no moral evil. God can bring it about that every actual person is a moral saint by creating a possible world that contains persons all of whose descriptions contain the element “actually makes morally relevant choices, makes them freely, and always makes them rightly.” If God makes only persons who correspond to descriptions of possible moral saints, no one will ever choose wrongly. Further, God will not have made them choose rightly; God will know that the recipes for possible persons are such that if the persons they are recipes for are created, those persons will freely always choose rightly. Therefore, these persons will be free agents in accord with Plantinga’s requirement.

The result of this line of reasoning is simply that if God exists, God will create only persons who freely always choose rightly. People do not always freely chose rightly, so God does not exist. Alternatively, if God exists, God will make actual only a possible world with persons all of whom are moral saints. The actual world does not contain persons any of whom, let alone all of whom, are moral saints, therefore, God does not exist.

The objection is cast in possible-worlds terms, and so is Plantinga’s reply. Consider a different element in the description of a possible person: “actually makes morally relevant choices, makes them freely, and sometimes makes them rightly” or, more simply, “freely makes some wrong morally relevant choices.” Suppose, as logically possible, that every person who was actually created would do this. The crucial point that the objector has missed is this: What can consistently go into a description is a matter of logic alone. However, what some actual person would do is not a matter of logic alone. Therefore, the description that would be true of an actually created person partly depends on what that person would do if he or she were created. It might well be that one thing the person would do is sometimes freely choose wrongly. This might well be true of absolutely every actual person God created. After all, it seems to be true of every actual person as things stand. Suppose it is true of absolutely every actual person God created—suppose whatever description of a person God made true by making the corresponding person will in fact have the result of there being a person who sometimes freely acts wrongly. Then, we might say (following Plantinga), possible persons suffer from transworld depravity.

Plantinga’s reply to the objection, then, is if it is logically possible that possible persons suffer from transworld depravity, then it is logically possible that God will not create only persons who are moral saints. It is logically possible there are not any possible moral saints to make actual. It is logically possible that possible persons suffer from transworld depravity. Hence, it is logically possible that God will not create only persons who are moral saints. However, if it is logically possible that God will not create only moral saints, then “God exists” does not after all entail “God creates only moral saints,” and therefore, the fact that the world is not populated only by morally perfect people is not evidence that there is no God.

Plantinga also presents what he takes to be a modestly successful version of the traditional ontological argument, which is intended to show that it is logically impossible that God not exist and hence logically necessary that God does exist. The argument, in Plantinga’s formulation, can be put succinctly as follows: Let a being who is omnipotent, omniscient, and morally perfect in some possible world W be maximally excellent—in W. Now consider a being who, for any possible world W*, is maximally excellent—in W*. Let this feature of having maximal excellence in every possible world be maximal greatness. The argument now takes advantage of this feature of propositions about all possible worlds, namely that they are, if possibly true, then necessarily true. Suppose P is a proposition about all possible worlds. Then either P is a necessary truth or a necessary falsehood. Suppose further that P is possibly true. Then P is not a necessary falsehood, and because it is either a necessary falsehood or a necessary truth, it is a necessary truth.

“God has maximal greatness” is a proposition about all possible worlds. Hence it is either a necessary truth or a necessary falsehood. However, it is not a self-contradiction; it is not a necessary falsehood. Therefore, it is a necessary truth, and it is true that God has maximal greatness, which entails that God exists in all possible worlds. Because God exists in all possible worlds, and the actual world is of course a possible world (if it were not possible, it would not be actual), God exists in the actual world. Further, no matter what world had been actual, God would have existed in it as well. So not only does God exist, but it is logically impossible that God not exist.

The problem with this argument is that it is not at all obvious that any of these three statements is self-contradictory:

(1) God has maximal greatness;

(2) God has maximal excellence in our world but lacks maximal greatness; or

(3) God has maximal excellence in every world in which God exists (in every world description that includes the claim that God exists, God is described as maximally excellent).

However, if either (2) or (3) is true, then (1) is false (and hence necessarily false). Plantinga’s ontological argument does not show, but rather assumes, that it is (1), not (2) or (3), that is true. Hence it does not prove that it is logically necessary that God exists or that God exists.

Plantinga is aware of this (he pointed it out when he presented the argument) and claimed a more modest success, namely that it is perfectly rational to believe that the premises of his version of the ontological argument are true, and (because the argument is plainly valid) also perfectly rational to believe that God exists.

Influence

Plantinga published significant work on the philosophy of religion as well as metaphysics and knowledge theory (epistemology). He also offered theories in the philosophy of language and modal logic. One of his common themes, nature of knowledge, was examined at length in his trilogy Warrant: The Current Debate, Warrant and Proper Function, and Warranted Christian Belief. Plantinga’s work in these areas has greatly influenced contemporary discussion on possible worlds, the problem of evil, the ontological argument, the notion of logical necessity, and the matter of when one is warranted in accepting something as true.

Additional Reading

Alston, William. Perceiving God. Ithaca, N.Y.: Cornell University Press, 1991. Offers a discussion of a wide variety of perspectives in the theory of knowledge by way of embracing the view that a theistic practice of belief formation can reasonably be believed to be reliable.

Dancy, Jonathan, and Ernest Sosa, eds. Blackwell Companions to Philosophy: A Companion to Epistemology. Oxford: Blackwell, 1992. A series of discussions of a wide variety of perspectives, theories, ideas, and arguments in theory of knowledge, including internalism and externalism.

Kvanvig, Jonathan L., ed. Warrant in Contemporary Epistemology: Essays in Honor of Plantinga’s Theory of Knowledge. Lanham, Md: Rowman and Littlefield, 1996. This collection of essays examines Plantinga’s views on warrant and proper function and his theory of knowledge. Includes bibliography and index.

Sosa, Ernest. Collected Essays in Epistemology. Cambridge, England: Cambridge University Press, 1991. Defends an account of knowledge in which one is justified within an environment and relative to a community of believers.

Tomberlin, James, and Peter van Inwagen, eds. Alvin Plantinga. Dordrecht: D. Reidel, 1985. Collection of essays on various aspects of Plantinga’s work, including the work that provided the background for the trilogy on warrant.

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