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.
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.
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...
(The entire section is 2968 words.)