Our Lord after his resurrection and before He ascended to heaven called together the disciples on a hill in Galilee and told them to teach all nations. Christ instructed them to teach all the doctrines, commandments and laws that He had taught to them. It is significant to note that these instructions are not constricted by the lifetimes of the disciples but was to be taught for all times which would be completed at the Parousia. This meant that the disciples were to have successors and that their oral teaching would be for all times protected by Christ which extended to their successors. In this way Christ assured that truth would be taught for all time to humanity. This was the great commission.
To those deep in Scriptures it seems quite odd that there are some who think that the disciples fulfilled their commission given to all by writing Scriptures and that they left no successors to continue the fullness of truth and the authority given by Christ in that commission. If this was the intent of our Lord it is odd that not all the disciples did what some suppose our Lord commanded which is to write Scriptures. In fact, only five disciples continued their teaching by writing Scripture. To those who believe that it is the Scriptures that continue the great commission then it is difficult to ignore that less than half of the disciples followed Christ’s commission. The disciple Matthew wrote a Gospel. John wrote a Gospel and three epistles. Peter wrote two epistles and James and Jude wrote one apiece. If the written Word was so important in Christ’s structure of the Church then it would be logical that there would be at least one epistle from Jesus; perhaps in which He would instruct us to give the written Word His only authority and not the 12 disciples as was His instructions in the great commission. But of course, it was obviously not His intent for His teaching to be spread only from written means but instead through the solid foundation He had built on which the disciples would continue to build with their successors which passed on the chrism from Christ through the disciples and their successors which has resulted in infallible truth for all times.
Another oddity for those who believe only in the written Word is why the Church founded by Christ existed for only a half century as a teaching Church and then is replaced by inspired books alone?
With changing circumstances it would seem reasonable that there be someone or some authority that can apply the apostolic teaching to the change of circumstances lest there be chaotic frustration instead of the application of truth. Take for example the doctrines; these doctrines may be studied with an almost equal danger of error as truth if there is no infallible teacher. An infallible authority would not restrict an enlightened development of truth for those who are seeking the question of what Christ meant in His teaching. Without it there is great possibility and indeed a certainty of error because there is not a word of Christ’s teaching that has not been subject to diverse interpretations. Many of these interpretations are compelling either by their scholarship or their application but are in contradiction of one another. Consequently the following question is illustrated by these facts; how are we to know the truth as these words surly are not enough for the truth to be known? Therefore it is necessary to have an infallible teacher to separate the diversity of opinions into the truth of Christ’s teaching. There must be revelation to satisfy the seeking soul instead of a growing set of diverse opinions and confusion. So, there must be an infallible teacher with the authority from Christ and of Christ as were the disciples for the truth to be known. The question is to those following Sola Scripture is whether the truth is essential or does it remain forever elusive depending on individual interpretation?
I believe the Scriptures demonstrate just how essential Jesus believed the truth to be. Before His death He gave certain men the authority to teach. He sent out the 72 disciples to teach with His authority. He said to them as well as the original 12, “He that hears you, hears me” which illustrates a transfer of the teaching by oral means to the Church across time to ensure the truth to all generations. It is through the oral teaching that the truth is found by the authority of Christ for truth. That truth is contained within the leadership of the Church and is today the Magisterium which is made up of the successors of those original disciples continuing the chrism given to them by Christ. God bless!