Koolhaas, Caspar often named with Koonmhert, in Holland, as the predecessor of Arminius, was born at Cologne in 1536. He studied at Diisseldorf, and in 1566 renounced many advantages to join the Reformation. He afterwards held some situations as pastor in the duchies of Zweibruck and Nassau. In 1574 he was called to the University of Leyden, then opening, as a professor. He subsequently resigned the professorship, and died a private teacher at Leyden in 1615. His opinions had been the cause of his resignation: he maintained nearly the same views professed afterwards by the Arminians on the extension of the authority of superiors in ecclesiastical affairs, reduction of the doctrine of the Church to a few simple, fundamental points, and the correction or absolute rejection of the doctrine of predestination. His work De jure Czristiani magistratus circa disciplimnam et regimen ecclesice gave great offence. He was summoned before a synod held at Middelburg in 1581, and requested to recant and sign the Belgian Confession, but refused, and appealed to the States. A provincial synod of Haarlem excommunicated him in 1582, but he was protected by the chief magistrate of Leyden, who reported to the Dutch States against the renewal of religious persecution, as well as against the acts of the synods, and the encroachments of the ecclesiastical college on the rights of the authorities. See A. Schweizer, Gescah. d. rej: Centraldogmen, ii, 40; Benthem, Holland Kirchen-u. Schulenstcat, ii, 33., Ugtenbogaert Kerkel. Hist. p. 214.-Herzog, Real-Encyklopadie, 8:26.