On an argument for the impossibility of miracles
I am not sure who first made this argument, but I found a reconstruction of it in my notes from 2010, when I taught Philosophy of Religion.
(1) A law of nature is something without exceptions.
(2) A miracle is an exception to a law of nature.
(3) There cannot be an exception to something without exceptions.
From (1) and (2):
(4) A miracle is an exception to something without exceptions.
From (3) and (4):
(5) There cannot be miracles.
Premise (2) is meant to be a definition. It originates from Hume and is attractive, because it is simple and, at first sight, plausible. But one might question whether it is a good definition.
If there is a person who is able to levitate, then it is not a law of nature that people cannot levitate, relying on (1), since the person with this ability is an exception and a law of nature has no exceptions. But even if you accept this reasoning, you might still be inclined to call it a miracle if you saw a person levitating. The inclination is, roughly, because you think of their levitating as beyond scientific comprehension and as having this quality because there is some divine power within the person or operating on them. One might think then that the definition of the concept of a miracle should reflect how we would use the word ‘miracle’, so that you can coherently speak of a miracle in this case.
Perhaps there are other responses to this argument, in particular responses that focus on (1), but they will not be detailed here.