Rupertus Meldenius, aka Peter Meiderlin, also called Peter Meuderlinus (born March 22, 1582 in Oberacker in Maulbronn; died June 1, 1651 in Augsburg) was a Lutheran theologian and educator.
The son of a Swabian priest, studied in Adelberg and after school visited the lower Konvikts in Maulbronn at the Tübinger Stift, where he met Johann Valentin Andreae. Meiderlin was a student of Mathias Haffenreffer and 1601 obtained a Master's degree. In 1605, he was at the Repentant convent in Tübingen, 1607, he assumed the Chair of the deceased philologist Martin Crusius. After a post as senior deacon in Kirchheim unter Teck, 1612, he was "Ephorus" of the Evangelical College of St. Anna in Augsburg. He held this office (with an interruption from 1630 to 1632), until 1650.
As a follower of the Concord, he defended the forerunner of Pietism, Johann Arndt in the confrontation about the orthodoxy of his teachings. In 1626 he published under the pseudonym Rupertus Meldenius a work entitled Paraenesis votiva per Pace Ecclesia ad Theologos Augustana Confessionis auctore Ruperto Meldenio Theologo (a reminder for peace at the Church of the Augsburg Confession of theologians), in which he wrote for peace among the contending parties and to unity within the meaning of the Concord and called to comply with charity (i.e. Christian love). In this context, he coined the phrase "In necessariis unitas, in dubiis libertas, in omnibus caritas" (In essentials unity, in doubtful things/non-essentials liberty, in all things charity).
… bedencken an die Herrn Kipperer und Geltwucherer …; Augsburg, 1623.