Frères de la vie commune
Haraeus first attended the Latin school of the Brethren of the Common Life in Utrecht and subsequently studied theology at the University of Louvain under Thomas Stapleton and Joannes Molanus. He was ordained a Roman Catholic priest at an early age, probably in 1578. He was appointed as a professor of rhetoric at the recently established University of Douai where he also obtained a Licentiate of Theology. In 1581 he accompanied the papal legate Antonio Possevino on an embassy to John III of Sweden and Ivan the Terrible.