Melanchthon inherited from his parents, Barbara Reuter and Georg Schwartzerd, a deep sense of piety that never left him. From his Bretten surroundings (where five citizens were burned as witches in 1504), he absorbed a sense of the occult that combined later with biblical references to stars, dreams, and devils to make him a firm believer in astrology and demonology. In 1508, within a period of 11 days, both his grandfather Reuter and his father died, his father after four years of invalidism.

While at the Universities of Heidelberg (1509–11; B.A.) and Tübingen (1512–14; M.A.), Melanchthon explored the teachings of Scholasticism, steeped himself in the rhetoric of the Dutch humanist Rodolphus Agricola (Agricola, Rodolphus) and the Nominalism of the English philosopher William of Ockham (Ockham, William of) and the ecclesiastical reformer John of Wesel, studied scripture, and read Classical works. On receiving the M.A. degree, he lectured, with conspicuous success, on the classics and soon had six books to his credit, including Rudiments of the Greek Language (1518), a grammar that was to go through many editions. He was praised by the great Dutch humanist Erasmus (Erasmus, Desiderius), and his name became known in England. In the best tradition of the time, Melanchthon was a humanist.

In 1518 Melanchthon accepted an invitation, relayed through Reuchlin, to become the University of Wittenberg's first professor of Greek. Only four days after his arrival, he addressed the university on “The Improvement of Studies,” boldly setting forth a humanistic program and calling for a return to Classical and Christian sources in order to regenerate theology and rejuvenate society.

Luther, the founder of the Protestant Reformation (Protestantism), and Melanchthon responded to each other enthusiastically, and their deep friendship developed. Melanchthon committed himself wholeheartedly to the new Evangelical cause, initiated the previous year when Luther circulated his Ninety-five Theses. (See Researcher's Note.) By the end of 1519 he had already defended scriptural authority against Luther's opponent Johann Eck (Eck, Johann), rejected (before Luther did) transubstantiation—the doctrine that the substance of the bread and wine in the Lord's Supper is changed into the body and blood of Christ—made justification by faith the keystone of his theology, and openly broken with Reuchlin.

During this time he had also published seven more small books and had earned the bachelor of theology degree at Wittenberg. His energy was phenomenal. He began his day at 2:00 AM and gave lectures, often to as many as 600 students, at 6:00. In addition, he found time to court Katherine Krapp, whom he married in 1520 and who bore him four children—Anna, Philipp, Georg, and Magdalen.

At Luther's urging, Melanchthon lectured on Paul's Letter to the Romans and in 1521 published the Loci communes rerum theologicarum (“Theological Commonplaces”), the first systematic treatment of Reformation thought. sin, law, and grace were the principal topics, with free will, vows, hope, confession, and other doctrines subsumed. Drawing on scripture, Melanchthon argued that sin is more than an external act; it reaches beyond reason into human will and emotions so that the individual human cannot simply resolve to do good works and earn merit before God. original sin is a native propensity, an inordinate self-concern tainting all man's actions. But God's grace consoles man with forgiveness, and man's works, though imperfect, are a response in joy and gratitude for divine benevolence. Three editions of the Loci communes appeared before the end of the year and 18 editions by 1525, in addition to printings of a German translation. The last edition in 1558 was much enlarged and changed. Luther declared that the Loci communes deserved a place in the canon of scriptures; the University of Cambridge in England later made it required reading, and Queen Elizabeth I virtually memorized it so she could converse about theology.

Despite an imperial decree of death to those who supported Luther, in 1521 Melanchthon sharply answered the Sorbonne's condemnation of 104 statements of Luther with “Against the Furious Decree of the Parisian Theologasters.” When Melanchthon hesitated to publish his lectures on Corinthians, Luther took a copy and published them in 1521 with a preface saying, “It is I who publish these annotations of yours, and send you to yourself.” In 1523 Luther did the same with Melanchthon's notes on John.

In 1521, during Luther's stay on the Wartburg, Melanchthon was the leader of the Reformation cause at Wittenberg. After the First Diet of Speyer (1526), where a precarious peace was patched up for the Reform movement, Melanchthon was chosen as one of the 28 commissioners to visit Saxony and regulate the constitution of the churches. In 1528 this resulted in the publication of Unterricht der Visitatoren (“Instructions for Visitors”), a set of instructions for the commissioners. In addition to a statement of Evangelical doctrine, it contained an outline of education for the elementary grades, which was enacted into law in Saxony to establish the first public school system. Melanchthon's educational plan was widely copied throughout Germany, and at least 56 cities asked his advice in founding schools. Through his lectures and textbooks, and the teachers he trained, Melanchthon exercised great influence in Protestant Germany. He helped found the universities of Königsberg, Jena, and Marburg and reformed those of Greifswald, Wittenberg, Cologne, Tübingen, Leipzig, Heidelberg, Rostock, and Frankfurt an der Oder. His efforts earned him the title “Preceptor of Germany.”

Melanchthon was present when the protest, from which the term Protestant originated, was lodged in the name of freedom of conscience against the Roman Catholic majority at the Second Diet of Speyer (1529). At the Diet of Augsburg (1530) Melanchthon was the leading representative of the Reformation, and it was he who prepared the Augsburg Confession, which influenced other credal statements in Protestantism. In the Confession he sought to be as inoffensive to the Catholics as possible while forcefully stating the Evangelical position. In the ensuing negotiations over adoption of the confessional statement, he seemed to compromise, but the vigour of his Apology of the Confession of (Apology of the Augsburg Confession) Augsburg (1531) belied any change. The Apology and Confession quickly became Lutheran symbols (authoritative statements of faith), as did one other Melanchthon treatise, his Treatise on the Power and Primacy of the Pope, which was an addition to the Schmalkaldic Articles of 1536–37, another Lutheran confessional statement. In the treatise, Melanchthon refuted historically and theologically any papal primacy by divine right but accepted papal jurisdiction as a human right for the sake of peace, if the Gospel were permitted. After the Diet of Augsburg further attempts were made to settle the Reformation controversies by compromise, and Melanchthon, from his conciliatory spirit and facility of access, appeared to the defenders of Roman Catholicism as the fittest of the Reformers with whom to deal. Despite frequent charges of collaboration with Roman Catholicism, Melanchthon staunchly upheld the tenets of justification by faith and scriptural authority.

The year after Luther's death, when the Battle of Mühlberg (1547) had dealt a seemingly crushing blow to the Protestant cause, an attempt was made to unite the Evangelicals and Roman Catholics in a provisional agreement, the Augsburg Interim. Melanchthon refused to accept the Interim until justification by faith was ensured as a fundamental doctrine. Then, for the sake of order and peace, he declared that those principles which did not violate justification by faith might be observed as adiaphora, or nonessentials. He allowed the necessity of good works to salvation, but not in the old sense of meriting righteousness; and he accepted the seven sacraments, but only as rites that had no inherent efficacy to salvation. Melanchthon was bitterly criticized by fellow Protestants for his conciliatory stand on the Interim. His later years were occupied with controversies within the Evangelical church and fruitless conferences with his Roman Catholic adversaries. He died in 1560 and was buried in Wittenberg beside Luther.

Melanchthon's literary facility, clear thought, and elegant style of expression made him the scribe of the Reformation and the representative of the Evangelicals at numerous colloquies. He never attained entire independence of Luther, though he gradually modified some of his positions. These modifications centred on the Eucharist, the human role in conversion, and the place of good works.

As late as 1530 Melanchthon agreed with Luther on the Eucharist, but his own views had begun to shift from Luther's, and the changes that Melanchthon introduced in 1540 in the 10th article of the Augsburg Confession indicated that his view on the Eucharist paralleled John Calvin (Calvin, John)'s.

Melanchthon also came to hold that humans play a part in conversion. At first, following Luther's cardinal doctrine of grace, Melanchthon seemed to reject free will, and he pushed the Augustinian doctrine of irresistible grace close to fatalism. However, his Commentaria in epistolam Pauli ad Colossenses (1527; Commentary on Colossians) implied a rejection of predestination, and by 1532 in the Commentarii in epistolam Pauli ad Romanos (Commentary on Romans) he spoke of the human struggle to accept or reject the love of God. In the 1535 edition of Loci communes he pointed out that the individual must at least accept the gift of God's salvation and that individuals are therefore responsible for their destiny. This view is clearly expressed in De anima (1540; “On the soul”): “God draws, but he draws him who is willing.”

Because of his interest in ethics, Melanchthon increasingly emphasized good works as the inevitable fruits of faith. Luther was disposed to make faith itself the principle of sanctification, but Melanchthon laid more stress on law. In his “Instructions for Visitors” articles of 1528 he urged pastors to instruct people in the necessity of repentance and to bring the threat of the law to bear upon men in order to instill faith. This brought upon him the opposition of the antinomian Johann Agricola. In the Loci communes of 1535 Melanchthon sought to put the fact of the coexistence of justification and good works in the believer on a secure basis by declaring the latter “necessary” to eternal life. For the sake of public order, Melanchthon was led to lay more and more stress upon the law and moral ideas, but his Evangelical position was that man is saved by faith and that good works are the “necessary” expression of faith, for good works flow from faith.