Alvin Plantinga offers at least two major solutions to the problem of divine action; that physical laws of the Newtonian sort are (often implicitly) qualified to apply only to causally closed systems, and that quantum physics has overtaken Newtonian physics as the fundamental description of the material world. Regarding the first solution, Plantinga states:

According to Newton and classical mechanics, natural laws describe how the world works when, or provided that the world is a closed (isolated) system, subject to no outside causal influence. In classical physics, the great conservation laws deduced from Newton's laws are stated for closed or isolated systems.

These principles, therefore, apply to isolated or closed systems. If so, however, there is nothing in them to prevent God from changing the velocity or direction of a particle. If he did so, obviously, energy would not be conserved in the system in question; but equally obviously, that system would not be closed, in which case the principle of conservation of energy would not apply to it. Indeed, there is nothing here to prevent God from miraculously parting the Red Sea, or bringing someone back to life, or, for that matter, creating ex nihilo a full-grown horse in the middle of Times Square. 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.

Furthermore, it is no part of Newtonian mechanics or classical science generally to declare that the material universe is a closed system. You won’t find that claim in physics textbooks—naturally enough, because that claim isn’t physics, but a theological or metaphysical add-on. (How could this question of the causal closure of the physical universe be addressed by scientific means?) Classical science, therefore, doesn’t assert or include causal closure. Moreover, the natural laws offer no threat to special divine action. 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 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. (Plantinga, Where the Conflict Really Lies, 2011, p. 78-79)

The idea here is that when properly qualified, the laws of physics are of the form "if/when/while the universe is causally closed, P," where the consequent P is, i.e., "nothing can accelerate from a speed less than to a speed greater than light."

Initially this seemed like a well presented solution, but I have since been informed that in science, any system which is not causally closed can never become causally closed again; once energy is added from the outside, its causal influence on the system is chaotic and the system is forever "open." Therefore, it would not make sense to talk about the consequent of some law not applying "when" or "while" the universe is causally closed. Rather, once a miracle occurred, no consequent of a law of classical physics would be applicable to the real world ever again. Of course, if we assess the "if" conditional, and just say the universe is not causally closed, then the consequents don't apply at all. Both implications seem absurd; laws are established for the exact purpose of describing the operation of the material world, and it's fairly clear that they don't suddenly stop applying after the first miracle in history.

Of course, the second solution would remain sound, and sufficient to undercut the problem of divine action, but the implications for the first solution would still be interesting. This objection seems far too easy to have evaded the mind of Plantinga. Why does it fail?

  • 1
    This seems like a really interesting questions -- when you say recently been informed that in science can you make clearer what you mean and why you take this informing to settle the question?
    – virmaior
    Commented Jun 22, 2016 at 4:15
  • do you mean "casual" and "casually" or "causal" and "causally"? Commented Jun 23, 2016 at 7:33
  • i like Plantinga. i particularly like it when he takes on the likes of Richard Dawkins (an excellent biologist and a lacking philosopher and unconvincing apologist). but i am not so impressed with this explanation from Alvin. Commented Jun 23, 2016 at 7:38
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    I agree with virmaior, you are giving too much credibility to "science" information. If God can "open" the system, He can also "close" it, and "science" would have nothing to say or object to.
    – Guill
    Commented Jun 30, 2016 at 6:43
  • Why would God need to break His own laws? Is He a bad planner? Did He make mistakes that now need correcting? The entire idea of Divine Action is weird. Does God have a 'to do; list? Is not the idea just a touch anthropomorphic? .
    – user20253
    Commented Apr 10, 2018 at 12:27

2 Answers 2


There's nothing in the laws of physics that prevents miracles from actually happening; they are a record of observations, closely compacted. Even physicists modify their own laws - Einstein-Cartan theory which adds torsion to gravity, speculate on particles that don't exist - the Klien-Gordan field, or dimensions that haven't been observed - superstring theory.

It's quite possible to modify the laws of physics, so a miracle happens and then to restore them.

Miracles, by their own nature, rarely occur, and thus aren't repeatable events that can be experimented upon, or thought on, in the same way that normal science is.

In Lewis's plural worlds, he makes room for gods and miracles, the only fixed thing is rationality, ie the intelligibility of the world.

  • ya know, i think we should just admit that a miracle in reality (whatever it might be) is a deviation from physical possibility. otherwise it's not a miracle. it's just a rare manifestation of science we don't know about or don't understand yet. Commented Jun 23, 2016 at 7:29

To see that causally closed systems need not become forever open once an agent interferes with the system externally, suppose I run a program on an isolated computer that performs a simple, but unending loop. That instantiated, looping program is a causally closed system.

Suppose I stop the program by turning off the computer. When I shut the computer off, I acted as an agent from outside the causally closed system. From the system’s perspective I might as well have performed a “divine miracle”.

Suppose I start up the computer again and also start the looping program. The looping program has not been affected by my "divine miracle" of stopping the computer earlier. The looping program is now just as closed as it originally was.

Plantinga makes an important point about the idea of causally closed systems and physics in the book you cite, Where the Conflict Really Lies, page 79:

...it is no part of Newtonian mechanics or classical science generally to declare that the material universe is a closed system. You won’t find that claim in physics textbooks--naturally enough, because that claim isn’t physics, but a theological or metaphysical add-on.

Being causally closed simply means being “subject to no outside causal influence”. We can assume systems are causally closed to simplify an analysis of them. We don’t know that any systems are actually causally closed unless we have set them up that way, such as computer programs or experiments.

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