GIOVANNI di Vesalia (Johann von Wesel). — Theologian, whose real name was Johann Rucherath or Richerath, born in Oberwesel at the beginning of the 15th century, died in Mainz in 1481. Nothing is known of his early youth; certain information about him begins only from 1440, the year in which he entered the University of Erfurt, where in 1445 he obtained the degree of magister artium, and later, on 15 November 1456, the doctorate in theology. He also taught there for some years, until in 1460 he went to Worms as a canon. He was also a professor of theology at Basel, but soon returned to Worms (1463) as preacher of the cathedral, an office he held until 1477, when he was deposed by Bishop Reinhard von Sickingen because of the scandal caused by his sermons, which were directed especially against the Church of Rome.
Soon afterward, however, he obtained a similar position in the cathedral of Mainz, whither he had been called by Archbishop Diether von Isenburg. Here he formed relations with a Bohemian Hussite, a certain Nicola, for whom he wrote the treatise Super modo obligationis legum humanarum ad quendam Nicola de Bohemia, intended for the Hussites. Summoned before a tribunal of theologians from the Universities of Cologne and Heidelberg, he retracted his errors (21 February 1479), but was nevertheless confined for life in the Augustinian convent in Mainz. The errors of G. di V. regarding the Church, which he considered an invisible society (*quam nemo sciat nisi Deus*), on indulgences, on predestination, on the cult of the saints, and on transubstantiation, correspond roughly CHUS (v.).
His writings, partly still unpublished, include: *Adversus indulgentias disputatio* (ed. Ch. W. F. Walch, in *Monumenta medii aevi*, II, 1, Göttingen 1757, pp. 111-156), directed against the papal indulgence for the Jubilee Year 1450; *Opusculum de auctoritate, officio et potestate patronum ecclesiasticorum* (ed. Walch, op. cit., II, 11, p. 142 ff.), in which he denounced the defects of both the higher and lower clergy; *De potestate ecclesiasticae*; *De indulgentiis* and *De Dei iudicio*, now lost. Finally, of doubtful attribution are the two treatises *De processione Spiritus Sancti* and *De peccato mortali*.