DENIS, or DIONYSIUS PETAVIUS, a French Jesuit of great erudition, was born at Orleans in the year 1583. His father, who was a man of learning, observing in his son strong parts and an excellent genius for letters, took every means in his power to improve them. He used to tell his son, that he ought to qualify himself so as to be able to attack and confound the giant of the Allophyle; meaning Joseph Scaliger, whose abilities and learning were allowed to have done much service to the Reformed. Young Petavius seems to have entered readily into his father's views; for he studied most intensely, and afterwards levelled much of his erudition against Scaliger. To the study of the belles lettres he joined that of the mathematics; and afterwards applied himself to a course of philosophy, which he commenced in the college of Orleans, and finished at Paris. He subsequently maintained theses in Greek, which was as familiar to him as Latin; and the Latin, it is said, he understood better than he did his vernacular language. When he was pretty well advanced in his studies, he had free access to the king's library, which he often visited on account of the Latin and Greek manuscripts. Amongst other advantages which attended his literary pursuits, may be reckoned the friendship of Isaac Casaubon, whom Henry IV. called to Paris in 1600. It was at Casaubon's instigation that Petavius, though then very young, undertook an edition of the works of Synesius, in which he corrected the Greek from the manuscripts, translated what yet remained to be translated into Latin, and wrote notes upon the whole. He was only nineteen years of age when he was made professor of philosophy in the university of Bourges; and he spent the two following years in studying the ancient philosophers and mathematicians. In 1604, when Morel, professor of Greek at Paris, published the works of St Chrysostom, some part of Petavius's labours on Synesius were added to them; and from the title we learn, that he then took the name of Pietus, which he afterwards changed into Petavius. His own edition of the works of Synesius did not appear till the year 1612.

He entered into the society of the Jesuits in 1605, and did great credit to it by his extensive and profound erudition. He became a zealous advocate of the Church of Rome; and there was no way of serving it more agreeable to him than that of criticising and assailing its adversaries. He was very bitter against Scaliger; nor did he even spare his friend Casaubon whenever the latter came in his way. Petavius excelled particularly in chronology; the learned world in general being indebted to him for some exact and nice disquisitions on this subject. His principal work, which is entitled Rationarium Temporum, is an abridgment of universal history, from the earliest times till the year 1632, arranged in chronological order, with references to proper authorities; and it was improved by Perizonius and others, who made several additions to it after his death. This eminent father, after a very laborious life, died at Paris about the close of the year 1652, aged sixty-nine.