Let us picture as vividly as we can the situation that would have arisen in the early Church after false teachers such as Arius (Arianism), Nestorius, and Pelagius had surfaced-if men such as Athanasius, Cyril, and Augustine had not stood up against them,. As early as the fourth and fifth centuries, the Church would have lost the primary article of the Christian faith. The foundation would have been removed from beneath it, and it wold have had to collapse. That would indeed have been impossible in light of the eternal counsel of God concerning the Church. Nonetheless, because of that very counsel, God had to awaken tools such as those teachers.
True, while they were alive, they were hated and persecuted as evil disturbers of Christendom, but for more than a thousand years their names were beacons, great witnesses for the saving truth-and in eternity they will shine on as the brightness of the sky and the stars forever and ever. Let no one, then, be discouraged from giving testimony on behalf of the truth just because someone mocks his ‘false spirit.’ Such claims come solely from unbelief.
Law & Gospel: How to Read and Apply the Bible by C. F. W. Walther (A Reader’s Edition)