Early Church: Heavily relied upon fresh eyewitness accounts of things that transpired. Used logic to combat the antagonizing counterparts to firmly establish their faith-based new religion. The Council of Nicea helped affirm normative, fundamental aspects of the Christian faith.
Medieval Church: Agustine and Aquinas run a muck on their intellectual contemporaries. Augstine helped explain the merits of ecclesiology, manergism, and reacted toward Pelagius. He did all of these things to help establish what faith meant for the medieval Christian. Aquinas made the five proofs for Christianity which helped, again, establish faith for his contemporaries.
Reformation: Luther really brought the house down in this era -- making sure that the faith of his fellow Christians was not succumbing to the works-based theology of the Catholic Church. He reminded Christians that personal salvation relied upon faith, not works.