Baius, Or De Bay, Michael, a Flemish theologian, born at Melin in Hainault in 1513, died Sept. 16, 1589. He was educated at the university of Louvain, in which he became a professor and ultimately chancellor. His zealous advocacy of the doctrine of St. Augustine brought him into collision with his colleagues, who in 1552 laid 18 of his most objectionable dogmas before the university of Paris, which in 1560 condemned 15 of them as heretical and the other three as false. Notwithstanding this decision, the Spanish court sent Baius as its representative to the council of Trent in 1563. In the two following years he published various controversial works, which called forth on Nov. 1, 1567, the denunciatory bull of Pope Pius V., which anathematized 76 of his favorite dogmas, but did not name him. Baius afterward recanted and professed obedience, was engaged a few years later in similar controversies, and made a second retraction in 1580. The contest was renewed from time to time until his death. His works were published at Cologne in 1696, and his doctrines subsequently became the basis of Jansenism.