If S Vincent of Lerins had never written his Commonitorium, I doubt if we ordinary chaps would have ever heard of him. As it is, there is a recurrent suspicion that he could be deemed a Western Orthodox whose theology lacked the precision which S Augustine brought, if he did, into some areas of Christian thought. The Tractarians liked S Vincent's insistence that orthodoxy consists of what has been believed semper et ubique et ab omnibus [always and everywhere and by all]. But this is because it enabled them to appeal to the consensus of the first millennium against the errors of both popery and protestantism. However, for such a purpose it is a somewhat broken reed. There have always been errors within the Christian community, so that as a standard of orthodoxy this rule is ineffective. If you want to tell an Arian that he is not a Catholic, quod semper quod ubique quod ab omnibus will simply inspire him to ask in exasperation whereabouts in the Scriptures and Tradition homoousios is to be found. An argumentative Gnostic might observe of the Gospel of S Luke that en pote ote ouk en.
It seems to have been for this reason that Vatican II, like much of the Magisterium, has fought shy of canonising 'the Vincentian Canon'. It made a rare appearance when the CDF explained the status of Ordinatio sacerdotalis (dealing with the Ordination of women) as a document to be adhered to semper et ubique et ab omnibus - thus interestingly treating it as a directive for the future rather than as a diagnostic rooted in the past.
But the other Vincentian imperative ... his statement that development in Doctrine must be eodem sensu eademque sententia ... has been transformed, by iteration, into a central piece of the Magisterium. You will find it in Ineffabilis Deus, by which in 1854 S Pius IX defined the dogma of the Immaculate Conception. It appears in the Constitution of Vatican I Dei filius (at the end, just before the anathemas). S Pius X's Pascendi Dominici gregis repeats (para 28) these words of Dei filius in its treatment of Modernism, and the phrase was incorporated into the Anti-Modernist Oath taken by all clergy until 1967. After B John XXIII used it in his highly significant and programmatic Address at the start of Vatican II, it was repeated in Gaudium et spes (para 62), and B John Paul II, interestingly, extended its use from Dogmatic to Moral Theology in Veritatis splendor (para 53). And, if the Rule of Believing really is established by the Rule of Praying, then eodem sensu eademque sententia is right at the heart, not only of Vatican II, but also of the 'Spirit of Vatican II' as enunciated by the post-Conciliar liturgical changes: it is to be read each year in the Liturgia Horarum (Vol 4 p299) ... which cropped up only a couple of days ago. It is not surprising that our Holy Father cited these words in his programmatic Address to the Roman Curia in 2005.
If Vatican II, as Porta fidei tells us, is a tutissimus index for the future, then eodem sensu eademque sententia is in turn a tutissimus index for discerning the true meaning of the Conciliar documents and their role in the life of the Church.