Niccolò Machiavelli
Discourses on the First Decade of Titus Livius (Chap. 1.56)
That when great Calamities are about to befall a City or Country, Signs are seen to presage, and Seers arise who foretell them.

Whence it happens I know not, but it is seen from examples both ancient and recent, that no grave calamity has ever befallen any city or country which has not been foretold by vision, by augury, by portent, or by some other Heaven-sent sign. And not to travel too far afield for evidence of this, every one knows that long before the invasion of Italy by Charles VIII. of France, his coming was foretold by the friar Girolamo Savonarola; and how, throughout the whole of Tuscany, the rumour ran that over Arezzo horsemen had been seen fighting in the air. And who is there who has not heard that before the death of the elder Lorenzo de' Medici, the highest pinnacle of the cathedral was rent by a thunderbolt, to the great injury of the building? Or who, again, but knows that shortly before Piero Soderini, whom the people of Florence had made gonfalonier for life, was deprived of his office and banished, the palace itself was struck by lightning?

Other instances might be cited, which, not to be tedious, I shall omit, and mention only a circumstance which Titus Livius tells us preceded the invasion of the Gauls. For he relates how a certain plebeian named Marcus Ceditius reported to the senate that as he passed by night along the Via Nova, he heard a voice louder than mortal, bidding him warn the magistrates that the Gauls were on their way to Rome.

The causes of such manifestations ought, I think, to be inquired into and explained by some one who has a knowledge, which I have not, of causes natural and supernatural. It may, however, be, as certain wise men say, that the air is filled with intelligent beings, to whom it is given to forecast future events; who, taking pity upon men, warn them beforehand by these signs to prepare for what awaits them. Be this as it may, certain it is that such warnings are given, and that always after them new and strange disasters befall nations.