In the time of the broad religious enthusiasm in the late Middle Ages, the theme of “unity between God and human person” developed among contemplative orders and also among lay people being led by their intense concern for the one-to-one relationship with God. However, this concern also often caused a negative view regarding the role of the Church and its doctrine. A current of heretical movements began among some radical sects, who insisted on the possibility of the human person’s direct unity with God without the intermediate role of the Church and Christ. The Church authorities tackled these doctrines of heresies by means of the councils and the Inquisition. Perhaps the most influential and decisive event initiated by the Church was the promulgation of the papal bull In agro dominico (1329), which condemned the teachings of the German Dominican Meister Eckhart (ca. 1260-1328). The fact that one of the main doctrinal issues of this bull was his understanding on Christology with regard to the theme of unity shows how seriously this matter was being apprehended by the Church at that time.
Even after the promulgation of the bull, however, there still followed some authors and preachers who continued to proclaim the theme of unity. The Brabantine Augustinian Jan van Ruusbroec (1293-1381) is one of the major figures. The notable point of his thought is that, while presenting the unity between God and human person as equal to Christ’s unity with God the Father on the level of love and blessedness, he also emphasized the transcendence of Christ’s position as a divine Person. This fact seems to lead us to the hypothesis that Ruusbroec was trying to restore the theme of unity on the basis of the orthodox Christian theology, especially of Christology. In the present article, we will examine his Middle Dutch treatise A Mirror of Eternal Blessedness (Een spieghel der eeuwigher salicheit), in which the Christ-centric ideas are more obviously presented than in his other works. By the textual analysis, we outline some important aspects of his Christology with regard to the theme of “unity between God and human person.”