Faustus Socinus, a Unitarian theologian, is one of the most important of the Italian religious exiles in Poland.

His acquisition in 1562 of the papers of his uncle Laelius Socinus (1525–62), a theologian suspected of heterodox views, has led him to adopt some of Laelius' proposals for the reformation of Christian doctrines and to become an anti-Trinitarian theologian.

Laelius' commentary on the prologue to the Gospel According to John presented Christ as the revealer of God's new creation and denied Christ's preexistence.

Faustus' own Explicatio primae partis primi capitis Ioannis (first edition published in Transylvania in 1567–68; “Explanation of the First Part of the First Chapter of John's Gospel”) and his manuscripts of 1578, De Jesu Christo Servatore (first published 1594; “On Jesus Christ, the Savior”) and De statu primi hominis ante lapsum (1578; “On the State of the First Man Before the Fall”), will be of subsequent influence, the first, particularly, in Transylvania and all three in Poland.