In the mid 17th century English Protestant divine William Chillingworth derided the concept of an unbroken apostolic tradition. In his book Religion of the Protestants, Chillingworth asserted that "There have been popes against popes: councils against councils: councils confirmed by popes against councils confirmed by popes: lastly the church of some ages against the church other ages" . This assertion attempts to negate the force of the Catholic argument that Protestantism is not a fitting expression of Christian unity, since Protestant sects contradict each other. Chillingworth argued that the Catholic "unanimous consent of the fathers" is a mere illusion, a dream of Catholic apologists. It was Chillingworth's argument in part that prompted Cardinal Newman to write his famous Essay on the Development of Christian Doctrine. Newman, like many Catholic apologists, responded to this attack referring the principles of the Vincentian Canon.
In a certain sense, Newman's Essay is nothing other than an elaboration of the principles of the Vincentian Canon. Most traditional Catholics are familiar with the famous Vincentian Canon, named after St. Vincent of Lerins (d. 445). The canon is a three-fold test to assess the orthodoxy of an idea, stating that only those things can be considered part of the Catholic deposit of faith which have been believed "everywhere, always, by all." The famed passage is found in Chapter 2 of his famous work the Commonitorium. Let us begin by examining the passage in context. Having begun by affirming the authority of the Sacred Scripture, St. Vincent goes on to explain why the Bible alone is not a sufficient guide to faith:
"But here some one perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join with it the authority of the Church's interpretation? For this reason—because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another; so that it seems to be capable of as many interpretations as there are interpreters. For Novatian expounds it one way, Sabellius another, Donatus another, Arius, Eunomius, Macedonius, another, Photinus, Apollinaris, Priscillian, another, Iovinian, Pelagius, Celestius, another, lastly, Nestorius another. Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation." 
Therefore Scripture cannot stand alone; it needs the "standard of Ecclesiastical and Catholic interpretation" to ensure it is being understood aright.
But does this not involve us in a reductio ad absurdam? If we need the Church's tradition to rightly interpret the Scripture, how do we know we are rightly interpreting the tradition? In other words, after admitting the necessity of a "standard of Ecclesiastical and Catholic interpretation", how do we determine what the authentic standard is?
Taking up this objection, St. Vincent goes on to explain, introducing his famous dictum:
"[I]n the Catholic Church itself, all possible care must be taken, that we hold that faith which has been believed everywhere, always, by all. For that is truly and in the strictest sense
Catholic, which, as the name itself and the reason of the thing declare, comprehends all universally. This rule we shall observe if we follow universality, antiquity, consent. We shall follow universality if we confess that one faith to be true, which the whole Church throughout the world confesses; antiquity, if we in no wise depart from those interpretations which it is manifest were notoriously held by our holy ancestors and fathers; consent, in like manner, if in antiquity itself we adhere to the consentient [unanimous] definitions and determinations of all, or at the least of almost all priests and doctors." 
This is where we get the phrase "unanimous consent of the fathers" as an expression of what is believed "everywhere, always, by all."
But of course, these phrases are all relative, because there are always exceptions; we can always cite one church where a particular doctrine was denied, or one period in history when it was called into question, or some doctor or even a saint who erred on a specific point. There is no unity of "everywhere, always, all", at least in the absolute sense. Given that fact, are we left with nothing beyond Chillingworth's opinion that the concept of "unanimous consent of the fathers" is ephemeral? Are we left with Chillingworth's conclusion that accepting Tradition means "popes against popes" and "councils against councils"?
Assuming we are not ready to grant Chillingworth's argument that there is no real unanimous consent of the fathers, but understanding that even a 'unanimous' consent will not be so in the absolute sense, what can we make of St. Vincent's canon? What does it mean practically speaking, and how do we determine when something was kept by "the whole Church", and what does this mean?
In his masterful study on clerical celibacy, The Apostolic Origins of Priestly Celibacy, Fr. Christian Cochini proposes five criteria for applying the Vincentian Canon. The context in which Fr. Cochini discusses this problem has to do with priestly celibacy, but these considerations are applicable to the study of any issue where there is a question of patristic consensus.
1. A point of doctrine or discipline can be said to be kept by the whole Church at a given time in its history if the majority of men who enjoy great moral and intellectual authority in the Church during that age share the same opinions about it. In the early Church, we would be referring to the most influential Fathers, the most eminent doctors and renowned bishops, credited by their contemporaries and posterity with exceptional value. Thus we do not need the totality of all the opinions of the churchmen of that age; those who were most important serve as spokesmen for the rest.
2. A point of doctrine or discipline can be said to be kept by the whole Church at a given time in its history if it is kept by the Apostolic Churches; i.e., above all, those churches founded by the Apostles. This is what St. Irenaeus meant when he said that "it is in any Church that it [the Tradition of the apostles] can be perceived by those who want to see the truth" . Again, it is necessary only to know the opinion of every apostolic church; just the opinions of the most important or more representative suffice, unless we have formal evidence to the contrary that other apostolic churches were in disagreement with them. For example, if we know Alexandria, Rome and Antioch were in agreement on a certain point, but Corinth, Ephesus and Philippi are silent, it is presumed these lesser apostolic churches are in agreement with the greater unless there is formal recorded testimony to the contrary.
3. A point of doctrine or discipline can be said to be kept by the whole Church at a given time in its history if it is found to be kept by all the bishops; and what is kept by the bishops is expressed in the acts of their regional synods and episcopal assemblies where they met to come to common conclusions deemed to be in continuity with tradition. The North African synods of the 3rd-5th centuries, the Gallic councils of the 5th century and the famed Spanish councils of the 6th-7th centuries are excellent examples of such synods. Of course, episcopal consent is even more perfectly reflected in the judgments of Ecumenical Councils, both in what was decided at the time of these Councils as well as how later generations of bishops interpreted the decisions of these Councils.
4. A point of doctrine or discipline can be said to be kept by the whole Church at a given time in its history if between that time and the Apostolic age there is no decision coming from any authorized hierarchical authority attesting to the existence of a contrary belief or practice. This could only be the authority of an ecumenical council or the Holy See; the decisions of local synods would not be enough to affirm that something was "always maintained" in the universal Church since these synods are limited in scope of time and space. A great example of this is infant baptism. Despite that is it not clearly attested in the 3rd century, there exists no authoritative opinions contrary to the practice from the Apostolic age till that time. Therefore we presume such practices to be Apostolic and held by the entire Church.
5. A point of doctrine or discipline can be said to be kept by the whole Church if during the same time the point in question was never contested in the name of a contrary tradition by any of the apostolic churches. If there has been a dispute, it needs to be examined whether this led to the recognition of two parallel traditions (as in the Quartodeciman quarrel between Polycarp and Pope Anicetus), or whether it led to one tradition being rejected, as in the case of the baptismal controversy between Pope Stephen and St. Cyprian, which was resolved in favor of the pope. When the point in question is contested only by groups or individuals out of communion with the apostolic churches, the possibility of an unbroken tradition is not thereby called into question, as certain points of dogma are always questioned by heretics.
If we follow these principles in applying the Vincentian Canon, we see that we do not wind up with the dilemma Chillingworth proposed. Rather, as Newman explained in his famous Essay, we are able to delineate a clear and uniform testimony from antiquity running like a golden thread throughout the ages of the Church, providing a clear consensus as to what is and is not part of the Deposit of Faith. There is clearly no analogy between the very real dilemma of the disunity of Protestant sects and the alleged "popes against popes" accusation of Chillingworth.
Related : The Problem of Catholic Unity
 Thomas Birch, The Works of W. Chillingworth (Hooker: Princeton University, 1840), 194
 St. Vincent of Lerins, Commonitorium, 2
 St. Irenaues, Adversus Haereses, III,2,1).