This is the fourth in a series of posts on Plantinga's new book. They are collected under the rubric Science and Religion. In the third chapter of Where the Conflict Really Lies, Plantinga addresses questions about divine action and divine intervention in the workings of nature. A miracle is such an intervention. But aren't miracles logically impossible? Plantinga doesn't cite Earman, but I will:
John Earman, Hume's Abject Failure: The Argument Against Miracles (Oxford 2000), p. 8, writes:
. . . if a miracle is a violation of a law of nature, then whether or not the violation is due to the intervention of the Deity, a miracle is logically impossible since, whatever else a law of nature is, it is an exceptionless regularity.
According to one way of thinking, miracles are violations of laws of nature. And so one may argue:
1. A miracle is an exception to a law of nature.
2. Every law of nature is an exceptionless regularity (though not conversely).
3. A miracle is an exception to an exceptionless regularity.
4. Miracles are logically impossible.
Please note that (2) merely states that whatever a law of nature is, it is an exceptionless regularity. Thus (2) does not commit one to a regularity theory of laws according to which laws are identified with exceptionless regularities. The idea is that any theory of (deterministic) laws would include the idea that a law is an exceptionless regularity.
The above argument seems to show that if miracles are to be logically possible they cannot be understood as violations of laws of nature. To avoid the conclusion one must deny (1). How then are miracles to be understood? Plantinga supplies an answer:
Miracles are often thought to be problematic, in that God, if he were to perform a miracle, would be involved in 'breaking,' going contrary to, abrogating, suspending, a natural law. But given this conception of law, if God were to perform a miracle, it wouldn't at all involve contravening a natural law. That is because, obviously, any occasion on which God performs a miracle is an occasion when the universe is not causally closed; and the laws say nothing about what happens when the universe is not causally closed. Indeed, on this conception it isn't even possible that God break a law of nature. (pp. 82-83)
As I understand him, Plantinga is saying that a miracle is not a divine suspension of a law of nature, but a divine suspension of causal closure. Conservation and other natural laws apply to isolated or closed systems (78). God cannot intervene without 'violating' closure; but that does not amount to a violation of a law since the laws hold only for closed systems. "It is entirely possible for God to create a full-grown horse in the middle of Times Square without violating the principle of conservation of energy. That is because the systems including the horse would not be closed or isolated." (79)
Plantinga is maintaining that it is logically impossible, impossible in the very strongest sense of the term, for anyone, including God, to contravene a law of nature. But it is logically possible that God contravene causal closure. This implies that causal closure is not a law of nature.
But isn't it a proposition of physics that the physical universe is causally closed, that every cause of a physical event is a physical event and that every effect of a physical event is a physical event? No, says Plantinga. Causal closure is a "metaphysical add-on," (79) not part of physics. That's right, as far as I can see. I would add that it is the mistake of scientism to think otherwise.
Whether or or not God ever intervenes in the physical world, I do it all the time. It's called mental causation. That it occurs is a plain fact; that mental causes are not identical to physical causes is not a plain fact, but very persuasively arguable, pace Jaegwon Kim. So if a frail reed such as the Maverick Philosopher can bring about the suspension of causal closure, then God should be able to pull it off as well. (This comparison with mental causation is mine, not Plantinga's.)