ARNISÆUS (Henningsus), a philosopher and physician of great reputation, about the beginning of the 17th century. He was born at Halberstadt in Germany, and was professor of physic in the university of Helmstedt. His political works are much esteemed. The most remarkable of them is his book De authoritate principum in populum semper inviolabili, printed at Frankfort in 1612. In this he maintains that the authority of princes ought not to be violated. He wrote also upon the same doctrine his three books De jure majestatis, printed at the same place in 1610; and his Reflectiones Politicae, printed at Frankfort in 1615. Having received an invitation to go to Denmark, he went thither, and was made counsellor and physician to the king. He travelled into France and England, and died in November 1635. Besides the pieces already mentioned, he wrote several philosophical, medicinal, and political treatises.