Vincent was a monk of Lérins (a famous island monastery off Cannes) in southern Gaul in the fifth century. His work is better known than his life. Under the pen name Peregrinus he wrote his 'Commonitorium' in 434, and he died before 450. St Eucherius of Lyons called him a holy man, outstanding in eloquence and knowledge.

The 'Commonitorium' gives a rule for telling heresy from true doctrine: Scripture first and, where that is not enough, the tradition of the Catholic Church, holding 'what has been believed everywhere, always and by all'. It also describes how doctrine can grow without changing. The source notes that he leaned toward the Semipelagian side against St Augustine, before the Church had settled that question.

3 Acts xiii., Roman Martyrology. 3 The Acts are so utterly fabulous that it is impossible to make out where and when these martyrs suffered, if they ever existed. There were some 252 of them, and when slain they suddenly vanished, and no trace of their bodies could be detected. The Acts inform us that they suffered under the Roman emperor Antoninus, who was struck dead by lightning, and his successor, the Emperor Leo.

Feast on 24 May, an ecclesiastical writer in Southern Gaul [roughly modern France and Belgium] in the fifth century. His work is much better known than his life. Almost all our information concerning him is contained in Gennadius, "De viris illustribus" (lxiv). He entered the monastery of Lérins (today Isle St. Honorat), where under the pseudonym of Peregrinus he wrote his "Commonitorium" (434). He died before 450, and probably shortly after 434. St. Eucherius of Lyons calls him a holy man, conspicuous for eloquence and knowledge; there is no reliable authority for identifying Vincent with Marius Mercator, but it is likely, if not certain, that he is the writer against whom Prosper, St. Augustine's friend, directs his "Responsiones ad capitula objectionum Vincentianarum". He was a Semipelagian and so opposed to the doctrine of St. Augustine. It is believed now that he uses against Augustine his great principle: "what all men have at all times and everywhere believed must be regarded as true". Living in a centre deeply imbued with Semipelagianism, Vincent's writings show several points of doctrine akin to Casian or to Faustus of Riez, who became Abbot of Lérins at the time Vincent wrote his "Commonitorium"; he uses technical expressions similar to those employed by the Semipelagians against Augustine; but, as Benedict XIV observes, that happened before the controversy was decided by the Church. The "Commonitorium" is Vincent's only certainly authentic work extant. The "Objectiones Vincentianae" are known to us only through Prosper's refutation. It seems probable that he collaborated, or at least inspired, the "Objectiones Gallorum", against which also Prosper writes his book. The work against Photinus, Apollinaris, Nestorius [Nestorius (d. c. 451), whose teaching split Christ into two persons; condemned at Ephesus in 431], etc., which he intended to compose (Commonitorium, xvi), has not been discovered, if it was ever written. The "Commonitorium", destined to help the author's memory and thus guide him in his belief according to the traditions of the Fathers, was intended to comprise two different commonitoria, the second of which no longer exists, except in the résumé at the end of the first, made by its author; Vincent complains that it had been stolen from him. Neither Gennadius, who wrote about 467-80, nor any known manuscripts, enable us to find any trace of it.

It is difficult to determine in what the second "Commonitorium" precisely differed from the first. The one preserved to us develops (chapters i-ii) a practical rule for distinguishing heresy from true doctrine, namely Holy Writ, and if this does not suffice, the tradition of the Catholic Church. Here is found the famous principle, the source of so much discussion particularly at the time of the Vatican Council, "Magnopere curandum est ut id teneatur quod ubique, quod semper, quod ab omnibus creditum est". Should some new doctrine arise in one part of the Church, Donatism for example, then firm adherence must be given to the belief of the Universal Church, and supposing the new doctrine to be of such nature as to contaminate almost the entirety of the latter, as did Arianism [followers of Arius, who taught that the Son is a created being, not fully God], then it is to antiquity one must cling; if even here some error is encountered, one must stand by the general councils and, in default of these, by the consent of those who at diverse times and in different places remained steadfast in the unanimity of the Catholic Faith (iii-iv). Applications of these principles have been made by St. Ambrose and the martyrs, in the struggle with the Donatists and the Arians; and by St. Stephen who fought against rebaptism; St. Paul also taught them (viii-ix). If God allows new doctrines, whether erroneous or heretical, to be taught by distinguished men, as for example Tertullian, Origen, Nestorius, Apollinaris, etc. (x-xix), it is but to test us. The Catholic admits none of these new-fangled doctrines, as we see from I Tim., vi, 20-21 (xx-xxii, xxiv). Not to remove all chance of progress in the faith, but that it may grow after the manner of the grain and the acorn, provided it be in the same sense, eodem sensu ac sententia; here comes the well known passage on dogmatic development. "crescat igitur. . ." (xxiii). The fact that heretics make use of the Bible in no way prevents them from being heretics, since they put it to a use that is bad, in a way worthy of the devil (xxv-xxvi). The Catholic interprets Scripture according to the rules given above (xxvii-xxviii). Then follows a recapitulation of the whole "Commonitorium" (xxix-xxx).

All this is written in a literary style, full of classical expressions, although the line of development is rather familiar and easy, multiplying digressions and always more and more communicative. The two chief ideas which have principally attracted attention in the whole book are those which concern faithfulness to Tradition (iii and xxix) and the progress of Catholic doctrine (xxiii). The first one, called very often the canon of Vincent of Lérins, which Newman considered as more fit to determine what is not then what is the Catholic doctrine, has been frequently involved in controversies. According to its author, this principle ought to decide the value of a new point of doctrine prior o the judgment of the Church. Vincent proposes it as a means of testing a novelty arising anywhere in a point of doctrine. This canon has been variously interpreted; some writers think that its true meaning is not that which answered Vincent's purpose, when making use of it against Augustine's ideas. It is hardly deniable that despite the lucidity of its formula, the explanation of the principle and its application to historical facts are not always easy; even theologians such as de San and Franzelin, who are generally in agreement in their views, are here at variance. Vincent clearly shows that his principle is to be understood is a relative and disjunctive sense, and not absolutely and by uniting the three criteria in one: ubique, semper, ab omnibus; antiquity is not to be understood in a relative meaning, but in the sense of a relative consensus of antiquity. When he speaks of the beliefs generally admitted, it is more difficult to settle whether he means beliefs explicitly or implicitly admitted; in the latter case the canon is true and applicable in both senses, affirmative (what is Catholic), and negative or exclusive (what is not Catholic); in the former, the canon is true and applicable in its affirmative bearing; but may it be said to be so in its negative or exclusive bearing, without placing Vincent completely at variance with all he says on the progress of revealed doctrine?