What did david hume believe a miricale was?

Answer 1

Hume thought that miracles were subjective experiences, and was highly sceptical of them, cf "Of Miracles"

"A miracle is a violation of the laws of nature; as a firm and unalterable experience has established these laws, proof against a miracle, from the very nature of the fact, is as entire as any argument from experience as can possibly be imagined. Why is it more than probable that all men must die; that lead can not, of itself remain suspended in the air; that fire consumes wood, and is extinguished by water; unless it be that these events are found agreeable to the laws of nature, and there is required a violation of these laws, or in other words, a miracle to prevent them? Nothing is esteemed a miracle, if it happen[s] in the common course of nature...

...There must, therefore, be a uniform experience against every miraculous event, otherwise the event would not merit that appellation." -David Hume

Hume thought that such uniform experience was indeed direct, and full proof against miracles.

He also was suspect of the absence of miracles, prodigies, and wonders in his time, and called into question "The reliability of the witnesses" of previous times. He was the first to apply the term atheist to himself in the modern sense of the word.

Answer 2

David Hume defined a miracle as a violation of the laws of nature. He argued that since the laws of nature are based on uniform human experience, it is always more reasonable to believe that the testimony of a miracle is mistaken rather than to believe that a miracle has actually occurred.