Philosophy: A Very Short Introduction

argument. It starts at a point we all know well, because we all frequently rely on things that other people have told us. Mostly there has been no problem, but occasionally what we were told turned out to be false. Occasionally we have heard contradictory things from two people, so we knew that at least one of them was wrong even if we never found out which. And we also know a little about what leads to false reports: self-interest, protection of others, defence of a cause dear to one’s heart, the wish to have a good story to tell, simple sincere mistake, uncritical belief of earlier reports, mischief, and so on. Most of us have sometime in our lives gone wrong in most of these ways ourselves, so that it isn’t just from observation of others (as some of Hume’s words might be taken to suggest) that we acquire this knowledge. We all know that human testimony is sometimes to be treated with caution, and under certain circumstances with a great deal of caution.
Suppose I were to tell you that last week I drove, on a normal weekday morning just before midday, right across London from north to south, and didn’t see a single person or vehicle on the way—not a car, not a bicycle, not a pedestrian; everyone just happened to be somewhere else as I was passing. You might wonder whether it was an absurdly exaggerated way of saying that the roads were unusually quiet, or whether I was testing your gullibility, or recounting a dream, or maybe going mad, but one option you would not seriously entertain is that what I had said was true. Almost anything, you would tell yourself, however unlikely, is more likely than that.
That would be very reasonable of you. Even if what I said was in fact true (which is just about conceivable, since nobody was under any compulsion to be on my route at that time, so they might all have decided to be somewhere else) it still wouldn’t be at all reasonable of you to believe it, if your only reason for believing it was that I had said so. Had you been with me and seen the empty streets yourself things might be different; but we are talking about the case in which you are reliant on my testimony.
Perhaps you can see the shape of Hume’s argument beginning to appear. Given what its role is to be in underpinning religious belief, a miraculous event must surely be one which our experience tells us is highly improbable. For if it were the sort of thing that can quite easily happen, then any old charlatan with a bit of luck or good timing could seize the opportunity to qualify as having divine authority. But if it is highly improbable, only the most reliable testimony will be strong enough to establish it. Forced to choose between two improbabilities the wise, who as Hume tells us proportion belief to evidence, will opt for the alternative they find less improbable. So this will have to be the testimony of such witnesses, that its falsehood would be more improbable than the occurrence of the events it relates. And that is a tall order, since, as we have seen, the events must be very improbable indeed.
Now this leaves it perfectly possible that we might, in theory, have testimonial evidence that was strong enough. But it is enough to create serious doubt whether we do, in fact, have adequate evidence for any miracle. We know that eyewitnesses can be mistaken, or intentionally deceived. Many of us have had the experience of finding ourselves in disagreement with someone else who was also an eyewitness to the events reported, often within a day or two of the events themselves. Many reports of the miraculous come to us from people who were not eyewitnesses, and were writing or speaking years after the events in question. Most such reports come from adherents of the religion which these alleged miracles are used to support. A court of law would take the possibility that witnesses of this kind were unreliable very seriously indeed—in some cases so seriously that it wouldn’t even be prepared to hear them testify.
Are there any reports of miracles which escape such doubts? It sounds as if we might have to trawl through the whole of recorded history to answer that question. But that, Hume thinks, won’t be necessary. For it isn’t just that a miracle has to be extremely improbable. It has to be in a sense impossible—contrary to a law of nature (‘instead of being only marvellous, . . . really miraculous’). That was Hume’s definition, and the one he expected his audience to accept. And this enables us to state the argument again in a slightly different, and more decisive, form—the form Hume preferred.
We receive a report of something—for convenience call it The Event—supposed to be miraculous. So we are asked to believe that The Event occurred, and that this was contrary to a law of nature. For us to have good reason to believe that an event of that kind would have been contrary to a law of nature, it must be contrary to all our experience, and to our best theories of how nature works. But if that is so then we have very strong reason to believe that The Event did not occur—in fact the strongest reason we ever do have for believing anything of that sort.
So what reason do we have on the other side—to believe that it did occur? Answer: the report—in other words the fact that it is said to have occurred. Could that possibly be so strong as to overpower the contrary reasons and win the day for The Event? No, says Hume, it could (in theory) be of equal strength, but never of greater. There might be such a thing as testimony, given by sufficiently well-placed witnesses, of the right sort of character, under the right sort of