David Hume
"David [ˈdeɪvɪd] Hume [ˈhjuːm] is one of the big figures in the Scottish Enlightenment [ɪnˈlaɪtnmənt]. He is most famous for developing a completely naturalistic [ˌnæʧrəˈlɪstɪk] philosophical system. This is a system that nowhere appeals to God in giving explanations of things. He is one of the first philosophers to ever have lots of things to say about almost all the different areas of philosophy but he does not appeal to anything supernatural in any of it. Hume's essay on miracles is a chapter in his book called, “An Enquiry [ɪnˈkwaɪəri] Concerning Human Understanding.”
Testimony
"Philosophers use the word ‘testimony’ [ˈtɛstɪməni] to refer to any situation in which you believe in something, on the basis of what someone else asserts, either verbally or in writing. Hume and other philosophers’ writing about testimony are going to point out that testimony is a really important source of beliefs for people. “There is no species of reasoning more common, more useful, and even necessary to human life, than that which is derived from the testimony of men”(Hume)."
False testimony
"False testimony is common because people are often wrong about things, and so their sincere testimony is mistaken. But it’s also common because people often have reason to assert falsehoods, as in when they are lying or joking."
Evidentialist principle
"Hume assumes that you should only trust testimony when you have evidence that the testifier is likely to be right. Hume thinks that this assumption follows from what seems like an innocuous assumption, sometimes called evidentialism [ˌɛvɪˈdɛnʃəlɪz(ə)m]: “A wise man … proportions his belief to the evidence.” You need evidence that people are generally reliable [rɪˈlaɪəbl], before you can trust people in general."
Cases where someone testifies to something unusual
"Hume says, the credit we give testimony “admits of a diminution[ˌdɪmɪˈnjuːʃən], greater or less, in proportion as the fact is more or less unusual.” So imagine that you go to a café and order a cup of coffee, and the waiter says that the coffee machine has broken. You’re likely to believe him. But now imagine that he says that aliens broke into the café last night and stole all their coffee. You’re likely not to believe him."
Hume on miracles
"For Hume, a miracle [ˈmɪrəkl] is an event that is an exception to a previously exceptionless regularity. It’s just something that has never happened before. Hume's conclusion is that you should never believe that a miracle has occurred on the basis of testimony. “No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavors to establish.”
Think again of the case of the café waiter. The reason that you’d be inclined not to believe his story about the aliens is that it’s more likely that the café waiter is wrong (for whatever reason) than that aliens really did steal his coffee. Hume argues that you should ask: what’s more likely, that the café waiter is wrong (for whatever reason), or that aliens really did steal his coffee? Or, as he puts it, what’s more “miraculous”: that aliens really did steal his coffee, or that this person is wrong (for whatever reason)?"
SOURCES
'Introduction to Philosophy' course (the University of Edinburgh)
https://www.coursera.org/learn/philosophy