9. The Book of the Sparkling Stone (_De Calculo, sive de Perfectione Filiorum Dei_).—This priceless work is said to have been written by Ruysbroeck at the request of a hermit, who wished for further light on the high matters of which it treats. It contains the finest flower of his thought, and shows perhaps more clearly than any other of his writings the mark of direct inspiration. Here again the scaffolding on which he builds is almost as old as Christian mysticism itself: that three-fold division of men into the ‘faithful servants, secret friends, and hidden sons’ of God, which descended through the centuries from Clement of Alexandria. But the tower which he raises with its help ascends to heights unreached by any other writer: to the point at which man is given the supreme gift of the Sparkling Stone, or Nature of Christ, the goal of human transcendence. I regard the ninth and tenth chapters of _The Sparkling Stone_—‘How we may become Hidden Sons of God and live the Contemplative Life,’ and ‘How we, though one with God, must eternally remain other than Him’—as the high-water mark of mystical literature. Nowhere else do we find such a marvellous combination of wide and soaring vision with the most delicate and intimate psychological analysis. The old mystic, sitting under his friendly tree, seems here to be gazing at and reporting to us the final secrets of that eternal world, where “the Incomprehensible Light enfolds and penetrates us, as the air is penetrated by the light of the sun.” There he tastes and apprehends, in ‘an unfathomable seeing and beholding,’ the inbreathing and the outbreathing of the Love of God—that double movement which controls the universe; yet knows, along with this great cosmic vision, that intimate and searching communion in which “the Beloved and the Lover are immersed wholly in love, and each is all to the other in possession and in rest.”