The 16th-17th century rationalist heresy founded by Italian uncle-and-nephew theologians Lelio Sozzini (1525-1562) and Fausto Sozzini (1539-1604), the latter giving the movement its name. Socinianism developed in Poland in the late 16th century and spread through pamphlet literature across Europe. Its core doctrines all denied historic Christian orthodoxy: the Trinity (one God in three persons) was rejected as irrational; the deity of Christ was denied (Christ a uniquely gifted man, but not God); the substitutionary atonement was repudiated (Christ's death was exemplary moral teaching, not satisfaction of divine justice); original sin was denied; and the doctrine of justification by imputed righteousness was abandoned. Socinian thought was the direct ancestor of 18th-century Unitarianism and 19th-century theological liberalism. Wherever the Trinitarian-incarnational-atonement core of orthodox faith has been quietly retired in modern mainline Protestantism, the underlying movement is Socinianism by a different name. The early Reformers (Calvin, Beza) and Reformed orthodox writers (Owen) wrote extensively against it.