The Mirror of Eternal Blessedness
Jan van Ruusbroec wrote this treatise in 1359, late in a long life spent first as a chaplain at St. Gudula's in Brussels and then as an Augustinian canon at the priory of Groenendaal in the Sonian Forest, where he had withdrawn in 1343. He composed it in Middle Dutch for a Poor Clare nun in Brussels, and its occasion is entirely practical: she had asked him how to receive Holy Communion well. The work is sometimes known as The Book of the Sacrament, and everything in it grows from that single request. It is spiritual direction addressed to one enclosed woman, written by a man who had spent decades watching what happens to souls who take the interior life seriously and what happens to those who counterfeit it.
Ruusbroec takes the words "Do this in remembrance of me" and unfolds from them the whole shape of Christian existence. Christ gives himself in the sacrament in flesh and in divinity, and the one who receives must give herself back in kind — so the treatise moves outward from the altar into obedience, self-denial, humility, and the ordinary discipline of a rule. Along the way he lays out the ascending pattern that governs all his writing: the active life of works, the interior life of yearning desire, and the God-seeing life of contemplation. But he refuses to let these separate. His most characteristic move is the insistence on what he calls the common life — the person who has been drawn into God's rest and yet flows out again to everyone in need, turning inward and outward in a single motion. Against this he sets a sharp warning about false rest: those who sit in natural emptiness, resting in their own bare being, calling their idleness union while producing neither love nor works. The title carries the argument's center of gravity. The eternal Son is the mirror in which the Father beholds himself and in which every creature is eternally seen; blessedness is to look into that mirror and find oneself already there.
Ruusbroec was translated into Latin by Willem Jordaens and by Geert Grote, who visited him at Groenendaal, and through Grote his writing shaped the Devotio Moderna and, by way of Hendrik Herp, reached later European contemplatives. The Mirror remains the most accessible entry into his thought because it stays tethered to a concrete question and a real reader.
Who should read this: anyone who wants Eucharistic devotion that is neither sentimental nor merely doctrinal, and anyone drawn to contemplation who needs to hear a master contemplative distinguish it from spiritual laziness. Readers seeking Ruusbroec's most speculative Trinitarian writing should go to The Spiritual Espousals instead; readers uninterested in monastic obedience and the concrete disciplines of enclosure will find much of this foreign.