St. Thomas Aquinas, a prominent Doctor of the Church, divided miracles into three types in his "Summa contra Gentiles":These works that are done by God outside the usual order assigned to things are wont to be called miracles: because we are astonished ("admiramur") at a thing when we see an effect without knowing the cause. And since at times one and the same cause is known to some and unknown to others, it happens that of several who see an effect, some are astonished and some not: thus an astronomer is not astonished when he sees an eclipse of the sun, for he knows the cause; whereas one who is ignorant of this science must needs wonder, since he knows not the cause. Wherefore it is wonderful to the latter but not to the former. Accordingly a thing is wonderful simply, when its cause is hidden simply: and this is what we mean by a miracle: something, to wit, that is wonderful in itself and not only in respect of this person or that. Now God is the cause which is hidden to every man simply: for we have proved above that in this state of life no man can comprehend Him by his intellect. Therefore properly speaking miracles are works done by God outside the order usually observed in things.