Some controversialists claim a need for an infallible interpreter for an infallible Bible therefore requires an infallible student. This shows a serious misunderstanding of the concept of infallibility. The human mind is designed to be able to discern the truth and it usually does. It is not necessary for it to be infallible to do so. The method of trial and error is sufficient. Unfortunately, there are limits to the ability of the human mind to learn the truth. In particular, the mind is strongly influenced by prejudices and presuppositions that may make some conclusions unacceptable. It is also possible to draw incorrect conclusions from fallacious use of the reasoning faculty. One may also draw improper conclusions from partial data. Furthermore, the mind may have problems comprehending those matters the content of which is beyond our immediate experience. Nevertheless, with proper guidance, preparation, and a good source of correct comprehensive information, the human mind is capable of coming to true knowledge without needing to be formally infallible itself.
Infallibility is not a guarantee that one will arrive at the full truth. Instead, it is a guarantee that the individual so endowed will not make any errors in what he says. Students learn from their mistakes. While it would be nice if they got everything right all the time, it is not necessary for them to do so in order to learn the truth. An infallible teacher merely guarantees that the student will not be presented with any erroneous information. The student can then use his intellectual powers to learn correctly what he has been taught. He may make mistakes, but with recourse to an infallible teacher and his natural intelligence, the average person can sort this out to arrive at true knowledge.
We must also draw a distinction between the different types of infallibility. The Bible is a static product. It is a text, not an authority. It cannot interpret itself. It is infallible in content but only when interpreted correctly. It cannot stand on its own. As the old saying goes, “A text without a context is a pretext.” Biblical infallibility is therefore contextual and not self-evident. As such the Bible is only materially infallible.
The Magisterium. on the other hand, is not a static text but a living authority under the direct superintendence of the Holy Spirit. It is dynamic and self-aware. It can respond to questions and because of the special privilege granted to it by God, it cannot err. God is the one who is both the formal and efficient cause of infallibility. This means that when the Magisterium operates in the proper context with the proper power acting on it (i.e., under the superintendence of the Holy Spirit) its statements are always infallible. The Magisterium is therefore the instrumental cause of infallible teaching.
Material infallibility is not sufficient to finally guarantee infallible teaching. You need to apply the proper context (formal cause: the plan of God) with the proper power (efficient cause: superintendence of the Holy Spirit) applied by the proper authority (the instrumental cause: the Magisterium) to obtain the desired end (final cause: true teaching). Once you have that, then the human mind can use its proper powers of discernment to learn the truth.
Some Protestant controversialists claim that the decision of the Catholic to believe in an infallible Magisterium is the equivalent of the individual claiming infallibility for himself. This is not true. If you go to the doctor and he tells you what must be done for your ailment, when you submit to his treatment, you are not declaring your own medical competence. You are recognizing his authority in medical matters and trusting in his judgment. In submitting to the Magisterium, we are deferring to the will of God as he has revealed it to his Church. We are not asserting our infallibility, but rather our faith in God’s promises.
When the Protestant reads his Bible and decides for himself what to believe, he is the one who is asserting his own infallibility because he is not submitting to any authority other than his own interpretation. If some Protestant group wishes to defer authority to its ministers or its confessional statements, it is asserting the infallibility of its ministers or founders over and against that of the historic Church. They often allege that they merely are asserting the infallibility of the Bible, but then we have the problem of settling disputes over discordant interpretations. It is the interpretation whose correctness is being questioned, not the correctness of the text it was based upon. As such, it must be the interpreter who needs to be infallible not the source which he interprets. As we noted in the previous section on perspicuity, it is not always possible to completely understand the biblical text even by the experts. Ultimately, the Protestant system is unworkable.
Quoted from Dr. Art Sippo