Arnold, Nicolaus, a Protestant theologian, was born at Lesna, in Poland, Dec. 17, 1618; died Oct. 15, 1680. He became, in 1639, rector of the school in Jablonow, and in 1654 succeeded Cocceius as- professor of theology at Franeker, where he became especially noted as a pulpit orator. His writings were chiefly polemical, e.g. Religio Sociniana refutata (Franeker, 1654, 4to):- Atheismus Socinianus (1659, 4to):-Discurs. theol. cont. Comeniu' (1660, 4to):-a refutation of the Catechism of the Socinians (Atheismus Socin;anus F. Bidalli refutatus, Amst. 1659):-a work entitled Lux in Tenebris (Light in Darkness), in which he explains those passages of Scripture which the Socinians use as arguments for their doctrines (Franeker, 1662, 2 vols.):- and a Commentary on the Epistle to the Hebrews.-Hoefer, Biog. Generale, iii, 326.