According to Hume, all knowledge of matters of fact comes from experience. A matter of fact on his view is basically anything that isn’t a mathematical or analytical truth. However, Hume acknowledges that though experience is the only guide in reasonings regarding matters of fact, it is not infallible; experience in some cases is less than uniform. ‘A wise man, therefore, proportions his belief to the evidence’ in cases where experience is not uniform (
Hume considers testimony as it relates to these epistemic norms. Experience provides the basis of our belief in human testimony (a consequence of experience providing us with the basis of all of our beliefs). We feel testimony to be reliable because we have experience with people as truth-tellers, and know by experience what psychological and social factors cause people to tell the truth, such as the general human inclination to tell the truth and the desire to avoid the shame of being exposed as a liar. Since testimony is founded on experience, its reliability should subject to the same measures of proof and probability as all other experimental evidence gathered from experience.
Testimonial reports of marvelous [which for Hume are unlikely but not impossible] and miraculous events are one source of positive evidence for their occurrence; in fact, since authority and tradition amount to forms of testimonial evidence, testimony is really the sole evidential ground for miracles for any person who has not witnessed a miracle herself. However, against the testimony in favor of a miracle we have our uniform experience of the world operating according to fixed laws; this experience serves as counterevidence to the possibility that the miraculous event reported might have occurred. Here we have two sources of evidence, both grounded in experience, in conflict. Our belief should side with the body of evidence that is more probable based on our experience.
Hume is making the empirical bet that in every case the evidence that the universe operates according to laws which prohibit the miraculous event will overwhelm the positive evidence for the miracle, which should be considered against the possibility that the story of the event is contrived, misunderstood, or misreported. Hume offers a maxim by which to evaluate miracle claims: the falsehood of the miracle report must be more miraculous than the miracle reported in order to warrant belief.
When we hear a report of a miracle, say, a man rising from the dead, we should weigh the probability of this occurrence against the probability that the testimony is false, and apportion our belief accordingly, which is to say, reject the miracle report as false.
Hume’s argument has not destroyed the possibility of miracles, of course. He has only shown that it’s irrational to believe in one if one takes the view that we ought to base our beliefs on the preponderance of evidence.
Claiming that the miracle is an act of God doesn’t increase its probability or weigh in its favor, according to Hume, since all we can know of God is known via nature, which speaks uniformly against the miraculous. The testimony of miracles is insufficient to found a religion, given that what grounds testimony in general also refutes it in the case of miracles. So the miraculous nature of any religion cannot be given as a defense of its veracity. Given that Christianity cannot be believed without at least one miracle, it is only faith that might compel assent to it, and this faith must be affirmed in opposition to reason, understanding, and experience.
Hume, D. An Enquiry Concerning Human Understanding (1772), ed. Tom L. Beauchamp. Oxford: Oxford University Press, 1999.