C.S. Lewis puts it pretty well in 'Miracles', a 1942 essay which seems to have been the seed that later grew into his book of the same name:
The experience of a miracle in fact requires two conditions. First we must believe in a normal stability of nature, which means we must recognise that the data offered by our sense recur in regular patterns. Secondly, we must believe in some reality beyond nature. When both beliefs are held, and not till then, we can approach with an open mind the various reports which claim that this super- or extra-natural reality has sometimes invaded and disturbed the sensuous content of space and time which make our 'natural' world. . .Granted, the absurdity of Herodotus' tale shouldn't lead us to automatically assume that the Biblical narrative is historically correct, but Lewis's basic point is sound: we can be absolutely confident that whatever thwarted the Assyrian invasion, it wasn't an overnight assault by a swarm of field-mice on their quivers, bowstrings, and shield-handles; we cannot be quite so confident about the behaviour of angels!
If we frankly accept this position and then turn to the evidence, we find, of course, that accounts of the supernatural meet us on every side. History is full of them -- often in the same documents which we accept wherever they do not report miracles. Respectable missionaries report them not infrequently. The whole Church of Rome claims their continued occurence. Intimate conversation elicits from almost every acquaintance at least one episode in his life which is what he would call 'queer' or 'rum'. No doubt most stories of miracles are unreliable; but then, as anyone can see by reading the papers, so are most stories of all events.
Each story must be taken on its merits: what one must not do is to rule out the supernatural as the one impossible explanation. Thus you may believe in the Mons Angels because you cannot find a sufficient number of sensible people who say they saw them. But if you found a sufficient number, it would, in my view, be unreasonable to explain this by collective hallucination. For we know enough of psychology to know that spontaneous unanimity in hallucination is very improbable, and we do not know enough of the supernatural to know that a manifestation of angels is equally improbable. The supernatural theory is the less improbable of the two.
When the Old Testament says that Sennacherib's invasion was stopped by angels (2 Kings 19:35), and Herodotus says it was stopped by a lot of mice who came and ate up all the bowstrings of his army (Hdt. 2.141), an open-minded man will be on the side of the angels. Unless you start by begging the question, there is nothing intrinsically unlikely in the existence of angels or in the action ascribed to them. But mice just don't do these things.
The first question, really, concerns whose side we take, Hamlet's or Horatio's. You know the line, of course: 'there are more things in Heaven and earth, Horatio, than are dreamt of in your philosphy'. If you accept that, than all manner of things can fall into place.
I found myself pondering this quite a bit last April, when the papers were awash with stories of the curing of Sister Marie-Simon-Pierre. It's worth reading Matthew Parris's response to this:
During Holy Week we are treated to a variety of decent-sounding people in print and on the airwaves explaining that religion — or “faith” as they now prefer to call it — is basically all about shared moral values, making the world a better place and gaining a proper sense of awe at life’s mystery. We are given to understand that the great world religions are all really fumbling towards the same truth.Well, maybe He didn't, though if Mr Parris really accepts the possibility that there's a He who didn't do this, I'm surprised he's so closed to the possibility that this same He might have done so had he so wished. After all, Parris hasn't answered the question he poses. How can he be sure? That demands an explanation of why he is so certain, and he doesn't provide one. Instead he just shouts louder. Assertion is, however, no substitute for argument.
And by doveish voices we are urged to join what is essentially a campaign for increasing the amount of goodness in the world. Who could be against that? Such faith sounds so reasonable. Churlish nonbelievers like me are made to feel it is we who are being arrogant, dogmatic, closed-minded. How can we be so sure? And then this. A nun has apparently been cured of Parkinson’s disease through writing the name of John Paul II on a piece of paper.
Ecclesiastical authorities in the Roman Catholic Church have been investigating the alleged miracle, interviewing neurologists, graphologists, psychiatrists and medical experts. The diocese of Aix-en-Provence is now satisfied that it has a putative supernatural intervention on its hands, and this week submitted its dossier to Pope Benedict XVI, who may declare an official miracle and begin procedures for making the late Pope a saint . . .
Where are you, intelligent Christians? Where is your voice, your righteous anger? Where is your honest contempt for this nonsense? Take that claimed recent miracle, for instance. I know lots of nice, clever Catholics — friends, thoughtful men and women, people of depth and subtlety, people of some delicacy, people who would surely cringe at the excesses of Lourdes. Do they believe that John Paul II may have cured this nun from beyond the grave?
Where are the shouts of self-respecting bishops and cardinal-archbishops, raised against the woeful confusion of faith with superstition? I have a theory about their reticence. I think they know this stuff is the petrol on which the motor of a great Church runs; that without these delusions to feed on, the unthinking masses would falter. And they may be right. But what a melancholy conclusion: that the thinking parts of a religion should be almost extraneous to what moves it; far from the core; just a little fastidious shudder; a wink exchanged between the occupants of the reserved pews.
There is, of course, an alternative: that they too believe the nonsense; that the Prime Minister’s wife (and maybe the Prime Minister), and the Communities Secretary, and the Chancellor of Oxford University and former Governor of Hong Kong — not to mention several of my colleagues on these pages in The Times — honestly entertain the possibility that from beyond the grave the late Pope John Paul II interceded with God to cause a woman to be cured of Parkinson’s disease.
You are living, dear reader, at a watershed in human history. This is the century during which, after 2,000 years of what has been a pretty bloody marriage, faith and reason must agree to part, citing irreconcilable differences . . .“But how can you be sure?” Oh boy, am I sure. Oh great quivering mountains of pious mumbo-jumbo, am I sure. Oh fathomless oceans of sanctified babble, am I sure. Words cannot express my confidence in the answer to the question whether God cured a nun because she wrote a Pope’s name down. He didn’t.
Let's look at the facts, as we know them. Back in 2001, a French nun was diagnosed with Parkinson's disease, and over time her symptoms worsened so that she could barely drive, walk, or write. By 2005, she could barely move the left side of her body at all, could hardly sleep for the pain, and could only write in an illegible scrawl. She couldn't bring herself to watch the aged John Paul II on television, trembling with Parkinson's himself. Her illness worsened after his death, and her order prayed for his intercession on her behalf. Then, one evening, she apparently heard a voice telling to take a pen and to write the name of the late pope. She did so, and was amazed at how her handwriting was clear and legible. She slept then, and woke the next day, at about half past four on the morning of 3 June 2005. She was cured.
I'm not saying that there's not another explanation for this, but it seems that nobody's got one. The whole scenario seems to be medically inexplicable. It really looks as though a miracle took place, and this possibility -- despite Parris's shouting -- can't be dismissed out of hand except on grounds of prejudice. Mark Shea tore into this impressively at the time, quoting extensively from chapter nine of Chesterton's Orthodoxy to do so. It's worth a read.
I've no idea what the miracle being associated with Newman is, by the way.