A better tack, I think, is to ask whether in fact miracles should be characterized as "violations of the laws of nature," as Newtonian mechanists assumed...An examination of the chief competing schools of thought concerning the notion of a natural law in fact reveals that on each theory the concept of a violation of a natural law is incoherent and that miracles need not be so defined. Broadly speaking, there are three main views of natural law today: the regularity theory, the nomic necessity theory, and the causal dispositions theory.15

According to the regularity theory, the "laws" of nature are not really laws at all, but just descriptions of the way things happen in the world. They describe the regularities which we observe in nature. Now since on such a theory a natural law is just a generalized description of whatever occurs in nature, it follows that no event which occurs can violate such a law. Instead, it just becomes part of the description. The law cannot be violated, because it just describes in a certain generalized form everything that does happen in nature.

According to the nomic necessity theory, natural laws are not merely descriptive, but tell us what can and cannot happen in the natural world. They allow us to make certain contrary-to-fact conditional judgments, such as "If the density of the universe were sufficiently high, it would have re-contracted long ago," which a purely descriptivist theory would not permit. Again, however, since natural laws are taken to be universal inductive generalizations, a violation of a natural law is no more possible on this theory than on the regularity theory. So long as natural laws are universal generalizations based on experience, they must take account of anything that happens and so would be revised should an event occur which the law did not permit.

Of course, in practice proponents of such theories do not treat natural laws so rigidly. Rather, natural laws are assumed to have implicit in them the assumption "all things being equal." That is to say, the law states what is the case under the assumption that no other natural factors are interfering. When a scientific anomaly occurs, it is usually assumed that some unknown natural factors are interfering, so that the law is neither violated nor revised. But suppose the law fails to describe or predict accurately because some supernatural factors are interfering? Clearly the implicit assumption of such laws is that no supernatural factors as well as no natural factors are interfering. Thus, if the law proves inaccurate in a particular case because God is acting, the law is neither violated nor revised. If God brings about some event which a law of nature fails to predict or describe, such an event cannot be characterized as a violation of a law of nature, since the law is valid only under the tacit assumption that no supernatural factors come into play in addition to the natural factors.

On such theories, then, if miracles are to be distinguished from both God's ordinary and special providential acts, then miracles ought to be defined as naturally impossible events, that is to say, events which cannot be produced by the natural causes operative at a certain time and place. Whether an event is a miracle is thus relative to a time and place. Given the natural causes operative at a certain time and place, for example, rain may be naturally inevitable or necessary, but on another occasion, rain may be naturally impossible. Of course, some events, say, the resurrection, may be absolutely miraculous in that they are at every time and place beyond the productive capacity of natural causes.

According to the causal dispositions theory, things in the world have different natures or essences, which include their causal dispositions to affect other things in certain ways, and natural laws are metaphysically necessary truths about what causal dispositions are possessed by various natural kinds of things. For example, "Salt has a disposition to dissolve in water" would state a natural law. If, due to God's action, some salt failed to dissolve in water, the natural law is not violated, because it is still true that salt has such a disposition. As a result of things' causal dispositions, certain deterministic natural propensities exist in nature, and when such a propensity is not impeded (by God or some other free agent), then we can speak of a natural necessity. On this theory, an event which is naturally necessary must and does actually occur, since the natural propensity will automatically issue in the event if it is not impeded. By the same token, a naturally impossible event cannot and does not actually occur. Hence, a miracle cannot be characterized on this theory as a naturally impossible event. Rather, a miracle is an event which results from causal interference with a natural propensity which is so strong that only a supernatural agent could impede it. The concept of miracle is essentially the same as under the previous two theories, namely, God's acting to cause an event in the sequence of natural events in the absence of any secondary cause of that event, but one just cannot call a miracle "naturally impossible" as those terms are defined in this theory; perhaps we could adopt instead the nomenclature "physically impossible" to characterize miracles.