I have previously detailed the historical importance of living prophets for a true church. Here we have an autobiographical account where Justin recollects that his own conversion to Christianity was set in motion when a certain old man addressed the following words to him in the course of a
philosophical conversation:

"A long time ago there lived certain men—much older than any of those so-called philosophers we have been talking about; blessed and righteous men, beloved of God. And they spoke by the Holy Spirit, foretelling those very things which are now coming to pass. They are called prophets. They are the only men who have ever seen the truth of things and told it to men without making any timid concessions to public opinion, without seeking to make an impression on people, and without being in the least influenced by concern for what other people might think of them. But, being filled with the Holy Ghost, they simply reported those things which they had seen and heard. The writings of those men survive to this day, and anyone can derive the greatest benefit from them, and learn from them about the beginnings and endings of things, and all such matters as philosophers are supposed to know. For it was not their wont to build up a case by formal argument, but simply to report the truth as reliable witnesses, without any disputation at all." ( Justin Martyr, Dialogue with Trypho 7, in PG 6:492. )
By Justin’s account, when he reported this conversation to a group of philosophy students, at this point of the story they disintegrated into mocking laughing—even for philosophers, it was just too funny for words. But Justin remained unmoved; for he saw clearly that only by revelation from outside and not through the speculation from within could man be freed from his fearful imprisonment within the narrow, dark chamber of his own restricted understanding/experience.