One may wonder why the empiricist philosopher David Hume, while stating that all reasonings concerning matters of fact depend entirely on experience, at the same time denies any truthfulness to miracles. Taking as his starting point the definition of a miracle as an exception to the laws of nature resulting from the will of God or some other invisible agent, Hume shifts the problem from that of belief in miracles to that of belief in witnesses. No matter how reliable a witness may be, her reports invariably concern a single, exceptional event, which by definition stands against the complete regularity of our experience of the laws of nature, whose evidence amounts to a proof (though not to certainty). Absolute singularity is only possible in a state which is either prior or external to human nature and experience, and for this reason could not be the basis of any belief. This is why, although Hume asserts that a miracle is always possible "a priori", he refuses from the start to accept to believe in the truth of any such reports, to wit, because of the alleged supernatural quality of the fact reported.