To be credible someone making an extra-ordinary claim, e.g. my neighbor can levitate, we would ask for evidence sufficient to the claim. It wouldn’t do to go on mere hear-say or my sincere insistence that my claim is true.
Extra-ordinary claims call for extra-ordinary evidence, or as David Hume stated: “A wise man proportions his belief to the evidence.”
“Suppose .. that the fact which testimony endeavors to establish partakes of the extra-ordinary and the marvelous: in that the evidence resulting from the testimony admits of a diminution, greater or less, in proportion as the fact [purported ‘fact’] is more or less unusual.”
(David Hume, Inquiry Concerning Human Understanding, “Section X “Of Miracles,” Part I”, 1748)
David Hume is regarded as a classical empiricist. Knowledge, if we have any, comes by way of experience. Along with this is the assumption that there are regularities in experience and nature.
It is surprising to critical thinkers that anyone would question the principle that measures the status of a belief to the evidence supporting it. The more extra-ordinary (marvelous, miraculous, magical) the purported event, the less weight carried by ordinary evidence (e.g., human testimony, reports, etc.).
It is not sufficient to well-grounded belief to affirm belief in miracles (e.g. a resurrection from death, or a feat of levitation) on testimony and reports of such events. Much more is called for if we’re to see such belief as rationally and empirically well-grounded.
Skepticism, not credulity, is the attitude of the rational person in the face of such extra-ordinary claims.
What could possibly be a philosophical rebuttal to this position skeptical of miraculous claims?
Some might raise technicalities about Hume’s suggestion of an appropriate proportion of evidence to belief. These would be questions as to the precise measured proportion: What objective standard could we apply to determine exact proportionality?
Some might object that supernatural possibilities that fall outside of human empirical knowledge are not judged in terms of evidence usually applicable only to ordinary events.
Some might bring up the fact that extra-ordinary claims in the sciences were not required to conform to a “proportionality of evidence” and were not rejected because of insufficient evidence for an extra-ordinary claim.
We can reply to each in turn. First Hume did not propose an exact science (with precise method and measurement) for evaluating extra-ordinary claims. Instead, he offered a practical, common sense guide for proceeding, i.e., a general “rule-of-thumb,” in a manner of speaking.
Many events which are seen as miraculous can be shown to have natural explanation and may result from illusion or hallucination. Those which cannot be readily explained do not automatically fall into the category of the miraculous. On the one hand, they might be events that await further investigation. On the other hand, they might be tagged (for now) as things we cannot presently explain. But our inability to explain or understand the event does not imply that miracle or magical event has occurred. All that is implied is that we do not presently have an explanation to give.
(Miracle: The intervention of a supernatural being into a natural or social happening, many times a happening that is beneficial for humans.)