A miracle is usually defined as an event brought about by divine action that would not have occurred in the ordinary course of nature. Reports of such events are close to universal across religious traditions, but the weight placed on them varies enormously, some traditions rest their central claims on miracles, and others treat them as marginal or as a distraction.
The scriptural vocabularies are instructive. The Hebrew Bible speaks of signs and wonders, above all in the Exodus narrative, where the point is the identification of the God who acts rather than the suspension of nature as such. The Gospels use signs, wonders and acts of power, and the Gospel of John consistently prefers "signs", presenting the miracles as pointing beyond themselves to who Jesus is. The Qur'an uses ayat, signs, for the miracles of earlier prophets, for the verses of the Qur'an itself, and for the ordinary regularities of nature, rain, growth, the alternation of night and day, which is a striking flattening of the distinction between the miraculous and the natural, and Islamic theology developed the doctrine of i'jaz al-Qur'an, the inimitability of the Qur'an, as the Prophet's standing miracle. Buddhist and Hindu texts report powers attained through meditative discipline, and both traditions treat attachment to them as a spiritual danger; the Buddha is depicted forbidding monks to display them to laypeople.
The modern philosophical argument turns on David Hume's essay "Of Miracles" (1748), which argued that testimony can never establish a miracle, since the uniform experience supporting a law of nature will always outweigh testimony against it, and since witnesses to the marvellous are characteristically credulous or interested. Replies have argued that Hume assumes what he needs to prove, that his handling of probability is defective, and that cumulative and independent testimony can outweigh a prior improbability. Spinoza had made a different objection: a violation of nature would be a violation of God's own decrees, and is therefore impossible. Theologians divide over whether a miracle is a suspension of natural law at all, Augustine held that a miracle is contrary not to nature but to what is known of nature, and much modern theology prefers to speak of God's action within a creation open to it rather than against a closed system.
Institutional practice reflects the range. The Catholic Church requires scientifically examined miracles for canonisation and maintains a medical bureau at Lourdes that has recognised a small number of cures out of many thousands of claims. Liberal Protestant theology since Schleiermacher, and programmatically in Rudolf Bultmann's demythologising, has often reinterpreted miracle narratives symbolically. Pentecostal and charismatic Christianity, which now numbers in the hundreds of millions and is the fastest-growing form of the religion, is built substantially on the expectation of present healing and miracle, and its growth is one of the reasons the topic is less marginal in contemporary religion than mid-twentieth-century predictions supposed.