Constantine’s deal? No such animal. The Church Fathers were left in charge precisely in order to prevent heresies and departures from the faith to occur.
http://www.geocities.com/catholic_profide/hrefute.htm is a translation from the Italian for a history of major heresies and how the Church dealt with them.
AUTHOR’S PREFACE. (St. Alphonsus M. Liguori)
1. — My object in writing this work is to prove that the Roman Catholic Church is the only true one among so many other Churches, and to show how carefully the Almighty guarded her, and brought her victoriously through all the persecutions of her enemies. Hence, as St. Iraeneus says (Lib. 3, cap. 3, n. 2), all should depend on the Roman Church as on their fountain and head. This is the Church founded by Jesus Christ, and propagated by the Apostles; and although in the commencement persecuted and contradicted by all, as the Jews said to St. Paul in Rome: “For as concerning this sect (thus they called the Church), we know that it is gainsayed every where” (Acts, xxviii, 22); still she always remained firm, not like the other false Churches, which in the beginning numbered many followers, but perished in the end, as we shall see in the course of this history, when we speak of the Arians, Nestorians, Eutychians, and Pelagians; and if any sect still reckons many followers, as the Mahometans, Lutherans, or Calvinists, it is easy to see that they are upheld, not by the love of truth, but either by popular ignorance, or relaxation of morals...
5. — St. Paul says: “There must be heresiees, that they also who are reproved may be made manifest among you” (I. Cor. ii, 19). St. Augustin, explaining this text, says that as fire is necessary to purify silver, and separate it from the dross, so heresies are necessary to prove the good Christians among the bad, and to separate the true from the false doctrine. The pride of the heretics makes them presume that they know the true faith, and that the Catholic Church is in error, but here is the mistake: our reason is not sufficient to tell us the true faith, since the truths of Divine Faith are above reason; we should, therefore, hold by that faith which God has revealed to his Church, and which the Church teaches, which is, as the Apostle says, “the pillar and the ground of truth” (I. Tim. iii, 15). Hence, as St. Iraeneus says, “It is necessary that all should depend on the Roman Church as their head and fountain; all Churches should agree with this Church on account of her priority of principality, for there the traditions delivered by the Apostles have always been preserved” (St. Iraen. lib, 3, c. 3); and by the tradition derived from the Apostles which the Church founded at Rome preserves, and the Faith preserved by the succession of the Bishops, we confound those who through blindness or an evil conscience draw false conclusions (Ibid). “Do you wish to know,” says St. Augustin, “which is the true Church of Christ? Count those priests who, in a regular succession have succeeded St. Peter., who is the Rock, against which the gates of hell will not prevail” (St. Aug. in Ps. contra part Donat.): and the holy Doctor alleges as one of the reasons which detain him in the Catholic Church, the succession of Bishops to the present time in the See of St. Peter” (Epis. fund, c. 4, n. 5); for in truth the uninterrupted succession from the Apostles and disciples is characteristic of the Catholic Church and of no other.
6. — It was the will of the Almighty that the Church in which the true faith was preserved should be one, that all the faithful might profess the one faith, but the devil, St. Cyprian says (2), invented heresies to destroy faith, and divide unity. The enemy has caused mankind to establish many different churches, so that each, following the faith of his own particular one, in opposition to that of others, the true faith might be confused, and as many false faiths formed as there are different churches, or rather different individuals. This is especially the case in England, where we see as many religions as families, and even families themselves divided in faith, each individual following his own. St. Cyprian, then, justly says that God has disposed that the true faith should be preserved in the Roman Church alone, so that there being but one Church there should be but one faith and one doctrine for all the faithful. St. Optatus Milevitanus, writing to Parmenianus, says, also: “You cannot be ignorant that the Episcopal Chair of St. Peter was first placed in the city of Rome, in which one chair unity is observed by all” (St. Opt. l. 2, cont. Parmen.)
(2) St. Cyprian de Unitate Ecclesie
7. — The heretics, too, boast of the unityy of their Churches, but St. Augustin says that it is unity against unity. “What unity,” says the Saint, “can all those churches have which are divided from the Catholic Church, which is the only true one; they are but as so many useless branches cut off from the Vine, the Catholic Church, which is always firmly rooted. This is the One, Holy, True, and Catholic Church, opposing all heresies; it may be opposed, but cannot be conquered. All heresies come forth from it, like useless shoots cut off from the vine, but it still remains firmly rooted in charity, and the gates of hell shall not prevail against it.” (St. Aug. lib. 1, de Symbol ad Cath. c. 6). St. Jerom says that the very fact of the heretics forming a Church apart from the Roman Church, is a proof, of itself, that they are followers of error, and disciples of the devil, described by the Apostle, as “giving heed to spirits of error and doctrines of devils” (I. Tim iv. 1).
8. — The Lutherans and Calvinists say, jusst as the Donatists did before them, that the Catholic Church preserved the true faith down to a certain period – some say to the third, some to the fourth, some to the fifth century – but that after that the true doctrine was corrupted, and the spouse of Christ became an adulteress. This supposition, however, refutes itself; for, granting that them Roman Catholic Church was the Church first founded by Christ, it could never fail, for our Saviour himself promised that the gates of hell never should prevail against it: “I say unto you that you are Peter, and on this Rock I will build my church, and the gates of hell shall not prevail against it” (Matt. xviii, 18). It being certain, then, that the Roman Catholic Church was the true one, as Gerard, one of the first ministers of Luther, admits (Gerard de Eccles. cap. 11, sec. 6) it to have been for the first five hundred years, and to have preserved the Apostolic doctrine during that period, it follows that it must always have remained so, for the spouse of Christ as St. Cyprian says, could never become an adulteress.
9. — The heretics, however, who, instead oof learning from the Church the dogmas they should believe, wish to teach her false and perverse dogmas of their own, say that they have the Scriptures on their side, which are the fountain of truth, not considering, as a learned author (3) justly remarks, that it is not by reading, but by understanding, them, that the truth can be found. Heretics of every sort avail themselves of the Scriptures to prove their errors, but we should not interpret the Scripture according to our own private opinions, which frequently lead us astray, but according to the teaching of the Holy Church which is appointed the Mistress of true doctrine, and to whom God has manifested the true sense of the Divine books. This is the Church, as the Apostle tells us, which has been appointed the pillar and the ground of truth: “that thou mayest know how thou oughtest to behave thyself in the house of God, which is the Church of the living God, the pillar and the ground of truth” (I. Tim. iii, 15.) Hence St. Leo says that the Catholic faith despises the errors of heretics barking against the Church, who deceived by the vanity of worldly wisdom, have departed from the truth of the Gospel — (St. Leo, Ser. 8, de Nat Dim.)...
(Arius) then began to promulgate the following blasphemies:— 1. That the Word was not from all eternity, but was brought forth out of nothing by the Father, and created, the same as one of ourselves; and, 2ndly, that Christ, according to his free will, was of a mutable nature, and that he might have followed vice, but that, as he embraced goodness, God, as a reward for his good works, made him a participator in the divine nature, and honoured him with the title of the Word, the Son, and of Wisdom (6).
Without the guidance of the Magisterium, we see various heresies recycled over time, given new names, and new twists and presented to the world as truth. Without the guidance of the Magisterium, we in fact do see that, as you indicate, that it IS possible to look at things this way or that, that Scripture alone can be interpreted a number of different ways, and that we have thousands of different interpretations from one (or two really) set of Scripture.
(You forgot to double-dog-dare ‘em to read it! ;^)