Socinians were members of the specific radical Reformation religious group that was formed originally in Poland in the XVIth century and went beyond the limited scope of the reform initiated by Luther or Calvin. At the roots of their religious doctrines was the Antitrinitarianism developed by Michael Servetus (1511-1553) and transplanted by Italian Humanists, and social ideas borrowed initially from the Anabaptists and Moravian Brethren. About the middle of the XVIth century a variety of Antitrinitarian sects emerged. They called themselves Christians or Brethren, hence Polish Brethren, also Minor Reformed Church. Their opponents labeled them after the old heresies as Sabellians, Samosatinians, Ebionites, Unitarians, and finally Arians. They were also known abroad as Socinians, after the Italian Faustus Socinus (1539-1604) (Fausto Sozzini, nephew of Leo Sozzini) who at the end of the XVIth century became a prominent figure in the Raków congregation for systematizing the doctrines of the Polish Brethren. Although the spirit of religious liberty was one of the elements of the Socinian doctrine, the persecution and coercion they met as a result of the Counter Reformation led them to formulate the most advanced ideas in the realm of human freedom and church-state relations. And it is in this respect that they made their great contribution as they broadened the impact of the Reformation into the political arena as well. These novel, rational ideas were opposed by both the reformed churches and the Catholic Church.
The ideas propagated by the Antitrinitarian Church and so convincingly expressed in their writings were very credible for political reasons as well. They had the advantage of coming from a small church, that could not aspire to influence the government and at the same time they were free from any sectarian spirit or bias, characterized only by independence of rational thought, absolute religious liberty, and profound patriotism and devotion to the state. The intellectual ferment Socinian ideas produced in all of Europe determined the future philosophical trends and led directly to the development of Enlightenment.
The precursor ideas of the Polish Brethren on religious freedom were later expanded, perfected and popularized by John Locke (1632-1704) in England and Pierre Bayle (1647-1706) in France and Holland. Their ideas on religious freedom, toleration, their philosophical and religious arguments, coincide with those used by the Polish philosophers. Locke possessed in his library works of earlier Antitrinitarians, works of Szlichtyng, Socinus, Smalcius, Wolzogen, Wiszowaty, Bibliotheca Fratrum Polonorum, Racovian Catechism, Przypkowski's Dissertatio de pace ... etc. He certainly read them and was influenced by them. Grandson of Jan Crell, Samuel Crell, was Locke's friend. Locke went further presenting a detailed analysis of toleration and state church relations from a political point of view, obviously under circumstances in England. Bayle makes numerous references to Socinians and their rationality. He was the first in the Christian world to separate ethics from religion and to defend atheism on a rational basis: "la foi n'influence pas sur la moralité" and "la moralité est indépendante de la religion." Locke's views on religious freedom were expressed first in 1667 in an Essay on Toleration that was not published during his life, and later in his four Letters on Toleration. Locke, however, did not develop the concept of complete separation of church and state. The other severe weakness of Locke's thought as well as of some statements of the Polish Brethren, was the exclusion of atheists.
The ideas of John Locke were transplanted directly to the American continent by James Madison and Thomas Jefferson who implemented them for the first time in the American legislation. They were philosophers-statesmen who shared a strong conviction for absolute freedom of conscience and distrusted any kind of established ecclesiastical institution. Their conviction was that the established churches create only "ignorance and corruption", introduce "diabolic principle of persecution." The exercise of religion should be completely separated from government, toleration was not enough only absolute freedom could be acceptable. Democracy understood as the institution erecting a "wall of separation" between church and state, and protecting the liberties of minority groups against the imposition of majority views was for them the best guarantee of religious freedom. Both were broadly educated and Thomas Jefferson had a keen interest in studying religions including the Socinians. Their writings follow Locke and quite echo the Socinian literature.
The Polish Brethren were forerunners of the later thinkers who developed ideas of the Enlightenment and humanistic modern times. Their doctrines, if allowed to develop, would probably bring true Enlightenment to Poland. Their achievements are the highest in Europe of their times and originated all modern trends in political, social and moral sciences, in biblical and religious studies, and in concepts of the absolute freedom of intellectual inquiry, liberty of conscience and complete nonantagonistic separation of church and state. They put to practice the highest ethical ideals. Their weakness lay in the neglect of political application.
The doctrines of the Polish Brethren represented a humanistic reaction to a medieval theology based on submission to the Church's totalitarian authority. Though they retained the scripture as something supra rationem, they analyzed it rationally and believed that nothing should be accepted contra rationem. Their social and political thought underwent a significant evolutionary process from the very utopian trend condemning participation in war and holding public and judicial office to a moderate and realistic stand based on mutual love, support of the secular power of the state, active participation in social and political life, and defense of social equality. They spoke out against the enserfment of peasants, a recurring issue in Poland not solved until the XXth century. They were the first to postulate the complete separation of church and state, an idea never before discussed in Christian societies. Their spirit of absolute religious freedom expressed in their practice and writings, "determined, more or less immediately, all the subsequent revolutions in favor of religious liberty." Their rationality set the trend for the philosophical ideas of the Enlightenment and determined future development of all modern intellectual endeavors. After expulsion they were forced into oblivion for three centuries, forgotten in a country that continued to be dominated by the Catholic Church.