One of the most distinguished theologians of the seventeenth century, born at Orléans, 1583; died at Paris, 11 December, 1652. He studied first at Orléans, then at Paris, where he successfully defended his theses for the degree of Master of Arts, not in Latin, but in Greek. After this he followed the theological lectures at the Sorbonne, and, on the advice of Ysambert, successfully applied for the chair of philosophy at Bourges. At Paris he became very intimate with Isaac Casaubon (see Letters MXXIV, MXXVIII, MXXXVIII, MXLIV), librarian at the Bibliothèque Royale, where he spent all his spare time studying the ancient Greek manuscripts. At Orléans he was ordained deacon and presented with a canonry. After spending two years at Bourges he returned to Paris, and entered into relations with Fronton du Duc, the editor of St. John Chrysostom. In 1605 he became a Jesuit, taught rhetoric at Reims (1609), La Flèche (1613), and at the College of Paris (1618). During this last period he began a correspondence with the Bishop of Orléans, Gabriel de Laubépine (Albaspinæus), on the first year of the primitive Church. From 1622 he taught positive theology for twenty-two years. During this time he was about to leave France on two occasions — first, to teach ecclesiastical history at Madrid at the invitation of Philip IV (1629), secondly to become a cardinal at Rome where Urban VIII wanted him (1639). At sixty years of age he stopped teaching, but retained his office of librarian, in which he had succeeded Fronton du Duc (1623), and consecrated the rest of his life to his great work, the "Dogmata theologica". The virtues of Pétau were not inferior to his talent; he was a model of humility and regularity, and, in spite of his feeble health, practised continual and severe mortifications. His ardent zeal for the Church inspired a rare talent to which his numerous works bear evidence; he devoted himself to the study of literature (Greek and Latin poets) and to other more erudite forms of learning.
The complete list of his works fills twenty-five columns in Sommervogel: he treats of chronology, history, philosophy, polemics, patristics, and history of dogma. The first edition of the works of Synesius appeared in 1612, undertaken ten years earlier at the advice of Casaubon ("Synesii episcopi Cyrenensis opera", new ed., 1633); in 1613 and 1614 the discourses of Themistius and Julian (new ed., 1630); in 1616 the "Breviarium historicum Nicephori"; then, after some poetical and oratorical works, an edition of St. Epiphanius in two volumes (1622; new ed., 1632), which had been undertaken at the advice of Jacques Gretser, S.J., and was originally intended only as a revised translation of Janus Cornarius. In 1622 and 1623 appeared the "Mastigophores", three pamphlets, and the notes dealing with Saumaise's "Tertullian", a bitter polemical work. Among his previous writings, Pétau had inserted some masterly dissertations on chronology; in 1627 he brought out his "De doctrina temporum", and later the "Tabulæ chronologicæ" (1628, 1629, 1633, 1657). It surpassed Scaliger's "De Emendatione temporum" (Paris, 1583), and prepared the ground for the works of the Benedictines. A summary of it appeared in 1633 (1635, 1641, etc.) under the title of "Rationarium temporum", of which numerous reprints and translations into French, English, and Italian have been made. About the same time (1636-44) appeared poetical works in Greek and in Latin and dissertations (often of a polemical nature) against Grotius, Saumaise, Arnauld, etc. His paraphrase of the Psalms in Greek verse was dedicated to Urban VIII (in 1637). Finally there appeared in 1643 the first three volumes of the "Dogmata theologica" (dated 1644); the fourth and fifth volumes were published in 1650. The work was incomplete at the death of the author, and, despite several attempts, was never continued. Numerous editions of the "Dogmata theologica" have been published, including that by the Calvinist Jean Le Clerc (Clericus, alias Theophile Alethinus), published in Antwerp (Amsterdam) in 1700; the last edition was brought out in eight volumes by J. B. Fournials (Paris, 1866-8). In 1757 F. A. Zaccaria, S.J. republished the work in Venice with notes, dissertations, etc.; in 1857 Passaglia and Schrader undertook a similar work, but they produced only the first volume. His letters, "Epistolarum libri tres", were published after his death; though far from being complete, they give an idea of his close acquaintance with the most famous men in France, Holland, Italy, etc.; they also furnish valuable information on the composition of his works and his method.
The reputation Pétau enjoyed during his lifetime was especially due to his work on chronology; numerous eulogies were pronounced on him by his contemporaries, such as Huet, Valois, Grotius, Isaac Voss, F. Clericus, Noris, etc. His chronological work has long since been surpassed, and a list of errors — inevitable at the period — could be drawn up even in the case of this man who boasted that he counted no less than eight thousand mistakes in the "Annals" of Baronius. But the great glory, which in the eyes of posterity surrounds the name of Pétau, is due to his patristic works and his importance in the history of dogma. With good reason he may be styled the "Father of the History of Dogma". The success of his work in this sphere was slow to make itself felt — it brought on the author accusations even from within his order — but it was highly esteemed by his pupils and far-seeing friends (e.g., H. Valois, Huet, etc.).
To form an opinion of Pétau's work it is necessary to go back to the period in which he wrote. It is far from being perfect and his criticism is more than once at fault. But his merit increases in spite of his shortcomings, when it is remembered that he had at hand only very imperfect editions of the Fathers, all inferior to the great masterpieces of the Benedictines; that many of the known texts only existed in translations, or in late and poorly studied manuscripts; that his predecessors in this line were few and practically everything had to be created. What he wanted had already been outlined by Melchior Cano in his work "De locis theologicis". Here we pass from theory to practice and we find a master at once. The originality of Pétau's work has been questioned; it may have been inspired, it is said, by a similar treatise of Oregius (died 1635), as Zöckler maintains, or by the "Confessio catholica" of John Gerhard (died 1627), as conjectured by Eckstein. But the "Confessio catholica" has a quite different aim, as is stated on the very first page; whole treatises, as for instance that on Christ, have but scanty quotations from three or four Fathers of the Church, and present nothing similar to the long historical developments of the sixteen books "De Incarnation, Verbi" of Pétau. The relationship with Cardinal Aug. Oregius, which rests solely on a conversation of a religious of the Minims of Dijon related in the "Voyage littéraire de deux bénédictins" (Paris, 1717, p. 147), has been examined in detail and completely disposed of by F. Oudin, S.J. in the "Mémoires de Trévoux" (July, 1718, pp. 109-33).
The state of religious strife during the days succeeding the Council of Trent drew all minds towards the primitive ages of the Church concerning which certain ancient documents were being discovered, while the excessive subtlety of many Scholastics of the decadence instigated a return towards positive sources. Pétau was no doubt inspired by the same ideas, but the execution of the work is completely his own. His aim and purpose are set forth by his dedicatory letter to the General of the Jesuits (Epist., III, liv), and in several parts of his "Prolegomena" (cf. I, i). His method reveals all the resources which the sciences of history. and philosophy have furnished to the theologians. He declares his opinion with full liberty as, e.g., concerning the opinion of St. Augustine on the problem of predestination, or the ideas on the Trinity of the ante-Nicene writers. Even for those who do not follow his historical plan the work has furnished a copious supply of documents; for theologians it has been a store of patristic arguments. We may here add that Pétau, like Cano, took the greatest pains with his literary style. He exaggerates the faults of Scholasticism; but on the other hand he defends it against the accusations of Erasmus. We still find the controversialist in the author of the "Dogmata"; after giving the history of each dogma, he adds the refutation of new errors. In his polemical writings his style was bitter; here and there he is more gentle, as when engaged in discussions with Grotius, who was drawing near the Catholic Faith. The memory of Pétau was celebrated the day after his death by Henri Valois, one of his best pupils, and by L. Allatius in a Greek poem composed at the request of Cardinal Barberini.