As soon as we take Hume’s definition of miracle: “violation of a law of nature”, we are thrown into the heart of the problem, because a law of nature is supposedly (according to Hume) fixed and regular, established by a uniform past experience.
For instance, I have always, when letting go of an object like a pen, experienced that object falling towards the ground. My past experience of that happening is entirely uniform. If one day I let go of a pen and it floated up to the ceiling I would be extremely shocked and probably conclude that a law of nature (gravity) had been broken.
However, given that neither I nor the vast majority of mankind have ever experienced this, not reported it to have happened, if someone told me that it had, I would, according to Hume, be unwise to believe them. I would use experience, observation, evidence and probability to examine the testimony of the levitating pen, and be forced to conclude that no such thing had happened.
From the nature of the case, given that it is more reasonable to believe what is more probable, it seems unreasonable to believe miracles have happened, as they are by definition highly improbable, because they supposedly go against a great mass of past experience.
So Hume says, for the wise man this high improbability amounts to a full proof against miracles. Notice that he doesn’t say it is a proof against miracles – merely that for all practical purposes the extreme improbability of it functions as a proof against it for those who are able to use reason correctly to weigh up testimonies for and against.
Therefore, you can view this ‘proof’ in two ways:
1. If you accept a definition of ‘proof’ to mean having considerable and weighty evidence for something, then you might be persuaded by Hume. This would be a looser definition than many require, but would still mean that something was highly likely to be the case.
2. However, on a more precise definition, proof means something more strict – an a priori state of affairs. As Ninian Smart says:
‘We cannot rule out a priori, i.e. without recourse to observing the way the world is, the possibility of miracles; and therefore we cannot frame a rule about believing in them which would rule out the legitimacy of believing what we see, if we were to see a miracle’
In other words, given that a miracle is a violation of a law of nature, but the only way we have to judge that a law of nature is actually a law is past experience, we are unable to rule out their impossibility, because at any point an experience may happen to us which goes against what has previously happened.
Another way of saying that is that laws of nature are not like judicial laws – they are not prescriptive but descriptive. In other words they don’t say what can and cannot happen, only what has or has not happened so far in our experience. This is called the problem of induction. Russell’s Turkey is a good way of remembering it.
So there are large flaws in Hume’s argument, if you are not willing to give him a little latitude with his definition of ‘proof’. But even if you are, there is also a problem with another definition – the ‘violation’ definition.
There is a paradox in the idea that a miracle actually disregards or violates the laws of nature, but if such a thing does occur, how can it be a law of nature – it no longer operates as a reliable occurrence all the time?
To finish I want to quote from an unknown source (I really must take note of where I get things from – if anyone knows who wrote this I will be happy to credit them!):
“Hume’s argument against miracles (if it doesn’t rely on an overly simplistic account of induction) goes through only if it is assumed from the outset that my religious beliefs (as well as other religious beliefs for that matter) are highly antecedently improbable from the outset. But Hume’s argument is intended to show that my beliefs (and other religious beliefs) are highly antecedently improbable from the outset. So Hume’s argument succeeds only if it begs the question.
Yes, of course, if you can show that my religious beliefs are highly improbable from the outset on grounds other than Hume’s argument, then you will have provided me with a good reason to be incredulous about those beliefs. But Hume’s argument itself fails, without begging the question at least, to accomplish what it was intended to accomplish, regardless of your success or lack thereof in that endeavor.”