elector of Brandenburg (1608-19), was born Nov. 18, 1572, and became noteworthy through his transition from the Lutheran to the Reformed Church. His father had endeavored to bind him to the support of the Formula of Concord (q.v.) by securing his signature to a declaration approving of that standard, and of' the existing organization in churches and schools. His wife, Anna, a daughter of duke Albert of Prussia and Maria Eleonore of Cleve, was a rigid Lutheran, and exercised all her influence to prevent a change in his Church relations; and the temper of many of his subjects in Brandenburg and the district of Prussia which he held as a fief from Poland threatened to render such a step productive of grave complications. To these influences must be added the certainty that many neighboring princes would withdraw their favor. Sigismund, nevertheless, took that step, and partook of the Lord's supper under the Reformed ritual, for the first time, on Christmas-day of 1613. Even his most embittered enemies never charged secular or political motives on him for this action, though a later generation adopted that explanation (Schrockh), He had been prejudiced against the Formula of Concord from the beginning, and had already, in 1610, issued statutes to the University of Frankfort, in which subscription to the Formula was not required. An immense excitement was caused. The elector of Saxony wrote, under date of Feb. 1, 1614, to dissuade Sigismund from completing the transfer; and on the 24th of the same month the latter was compelled to issue all edict forbidding the clergy to inveigh against his measures in the pulpit. The estates of Brandenburg demanded the continuation of the prerogatives enjoyed by the Lutheran Church, and the disuse of all measures intended to favor the Reformed. The difficulty was finally composed by the action of the elector, who (Feb. 5, 1615) engaged that the Lutherans should continue to enjoy liberty of conscience and to exercise the right of patronage where legally entitled thereto; but insured like privileges to their Reformed opponents. A colloquium of clergymen was held at Berlin in October, 1614, where the resolution was reached that defamation of the Reformed party should thereafter be avoided. The result of the whole contest was that the Reformed Church obtained legal recognition. Soon after his entrance into the Reformed communion the elector published his Confession of Faith (Joh. Sigism. (Confessio Fidei), May, 1614. It claims to deal with points at issue between Evangelical Protestants only. Its introduction disclaims the intention of introducing novelties, but asserts the necessity for removing certain remainders of popery, and concludes with a recognition of the sole authority of the Word of God and an approval of the "Apostolical, the Athanasian, and the Nicene, Ephesian. and Chalcedonian symbols;" to which list is added the Augsburg Confession of 1530, but as afterwards revised and improved. The Confessio. rejects all later Lutheran additions as the ubiquity of Christ's body, the involving of Christ's Deity in his passion, and the ascription of omnipotence to his humanity, etc. The remaining articles relate to the sacraments and the election of grace, and are entirely in accord with the ordinary Reformed, Calvinian view. See Hering, Hist. Nachr.. v. d. ersten Anfange d. evang. ref. Kirche in Brandenb. u. Preussen (177'8); Kuister, Altes u. Neues (Berlin); Von Mohler, Gesch. d. evangel. Kirchenverfassung in d. Mark Brandenburg (1846); Moller, Job. Siq. Uebertritt zum ref. -Bekenntniss, in the Deutsche Zeitschrit (Berlin, 1858), p. 189 sq.; and various Essays by prorector Schmidt, of Schweidnitz, etc.