When I was an agnostic/atheist college student and very much on the outside looking in, I took a course on early Christian thought. Although I was not converted (that came later), I came away convinced that the Church had in the early centuries been challenged by a series of potentially destructive heresies and had each time some how been able to get it right. After I converted, I found that G.K. Chesterton had long before me discovered the same miracle. He pointed out how, when attacked from the right and from the left, the Church had not come to some compromise, some gray middle ground, but had rather wondrously, divinely, reconciled the extremes by embracing them both.
God was not an unapproachable singularity or a series of emanation, but a Trinity of three equal persons in one perfect Godhead. Jesus was not just a man, or a demi-god or a shell in which God dwelt, but true God and true man. The Church delighted in the magnificence of St. Peter's and honored the stark poverty of St. Francis of Assisi. The Church defended both fruitful marriage and celibacy for the sake of the kingdom. And the Church has protected and promoted true personal freedom by providing a hierarchical structure through which the individual can be assured of finding answers to the most difficult theological questions, the intimacy of the sacramental presence of her Lord, and assurance of the forgiveness of sins.
Since the first days of the Church controversies have arisen. Believers have taken both sides, but Christians were not left in confusion, rather Christ endowed his Church with a system for deciding which side was right, for the Church is built on a rock -- on the successor to Peter alone and with his bishops in Council. Debates may go on for a while, each side making its case, but there comes a time when a decision must be made, and time and time again for 20 centuries history shows that the Church has by grace made the right decision. Because of this divinely instituted decision-making system, the faithful have the freedom to live in the truth.
We can see what happens when believers are denied this protection in the situation of our separated brethren. It is not just that they are separated from the Chair of Peter, when disputes arise, they lack the means to definitively resolve differences and their fellowships break into pieces.
St. Paul foresaw when he wrote. "I hear that there are divisions among you and I partly believe it. For there must also be heresies among you, that they which are approved may be made manifest..." (I Cor. 11:17)