In Handbook of Christian Apologetics, Kreeft and Tacelli write (p. 109):
“A miracle is a striking and religiously significant intervention of God in the system of natural causes. [… T]he concept of miracles presupposes, rather than sets aside, the idea that nature is a self-contained system of natural causes. Unless there are regularities, there can be no exceptions to them.”
Consider that the natural system (featuring causal processes unfolding in time and space) has a beginning. What caused it to begin? It is reasonable to posit that something caused it to begin. This something would be in some sense prior to (but not temporally prior, as time is a feature of the system) the natural system. If that something can create the natural system, then it doesn’t seem implausible, a priori, that it would be able to affect the system at various points. A simple metaphor for this might be someone who creates a game with its own rules that can play out (such as Conway’s Life) but then also steps in at various points to change the configuration of the game.
So far, this makes some sense. It is not conceptually problematic, in the broadest of brushes, to think this possible. The next question then becomes whether miracles (so defined) have, in fact, occurred.
This is where things get problematic. If miraculous causal events are those which aren’t determined by the system of natural causes running endogenously, but rather (at least partially) through an externally (so to speak) originating cause, then how could we tell which causes are of this latter type?
Consider Kreeft in The Philosophy of Tolkien (p. 54):
“It is easy to identify miracles when we see them[.]”
He does not elaborate. Yet, is it obvious? How can one distinguish between causes that originate external to the system, and those that are part of the system? Consider the notion that a significantly advanced technology could be considered ‘magic’ by those who don’t understand the technology, or the general conceptual backdrop for the technology. Since we don’t understand how the natural causal system works (and probably aren’t even close), why should we think that we can tell what are natural causal events and which are not?