1. Bible-only Christianity - The Roman Catholic Church teaches that the Bible and the traditions of the Church, as expressed in the decrees of popes and councils, etc. are authoritative. The reformers believed that the Scriptures, not church traditions, were the final authority for faith and practice. Martin Luther proclaimed that “...unless I am convicted of error by the testimony of Scripture or...by manifest reasoning I stand convicted by the Scriptures to which I have appealed, and my conscience is taken captive by God’s Word ...”
2. Justification by faith alone - The Roman Church had placed the merit of good works alongside faith as a requirement to obtain salvation. The reformers taught the Biblical doctrine that salvation comes by the free and undeserved grace of Christ. Good works are the product and evidence of justification, not a requirement for justification.
3. The priesthood of all believers - The reformers argued that there was no precedent in the early church for the priest as a mediator between the lay people and Christ. Each believer could confess his sins to and receive forgiveness from Christ without the aid of a priest. Each believer had the right and duty to read the Scriptures and trust the Holy Spirit to lead them into the truth.
On October 31st, 1517, Martin Luther nailed his 95 Thesis (reasons against selling indulgences to the north door of the Castle Church in Whittenburg, Germany. While the world celebrates ghosts, goblins, and ghouls, we can take time to remember reformers like Peter Waldo, Jan Huss, Martin Bucer, William Tyndale, Philip Melanchthon, Hieronymus Zanchius, John Wycliffe, Martin Luther, Guillaume Farel, John Calvin, William Perkins, Michael Satteeler, Matthius Illyricus, Theodore Beza, Heinrich Bullinger, John Knox, Urich Zwingli, Peter Vermigli, and Johann Oecolampadius who bravely called for the Church to return to the pure and undefiled New Testament gospel of Christ. Imperfect men (and women) who sought to follow the true Gospel.