People marvel at … things only because they rarely happen; but the causes for these are as apparent as for others … For example, at night a fearful man who sees a wolf in the fields, or a cat in his room, will immediately assert and judge that it is an enemy or a devil … because he fixes his imagination on these and fears them. And a person devout and rapt [in ecstasy] will judge that it is an angel … A vigorous imagining of a retained species, then, together with a small external appearance or with an imbalance of some internal disposition … produces marvelous appearances in healthy as well as in sick people.

Nicole Oresme and The Marvels of Nature, Bert Hansen's translation (Pontifical Institute of Mediaeval Studies, 1985), p. 73. - De causis mirabilium (c. 1370)