The author of this slender but profound book, a Cistercian monk, discovered as a young man the work of his fellow countryman Reni Guinon, whose writings introduced him to genuine metaphysical doctrine and to possibilities of spiritual realization. This discovery marked him indelibly, and he resolved to follow a monastic path in order to be free for the 'one thing needful'. The word Advaita, which designates Vedantic non-dualism, is Sanskrit for 'non-dual' or 'not two'; but the doctrine itself is by no means exclusively Hindu, being present in Buddhism, Islam, Taoism, and Judaism. In Christianity it has always been more implicit, though explicit with writers such as Dionysius the Areopagite, Eriugena, Eckhart, and even Dante. The great merit of this work by 'a Monk of the West' is that it shows that non-dualism is neither pantheism nor monism, and that there is no incompatibility between orthodox Christian doctrine and the strictest understanding of non-dualism in the Advaita Vedanta. The implication is that,non-dualism can again find expression within a Christian ambiance. The cover design helps clarify this. In the background is the Omkara, the sacred monosyllable of Hinduism, considered the most funadamental of affirmations. In the foreground is the Christian symbol of the Chi-Rho, chrismon, or labarum, consisting of the first two letters-chi (X) and rho (P)-of the Greek Christos, XRISTOS. This figure is intrinsically three-dimensional but is usually projected onto a plane surface. The cruciform Greek letter chi (X) is placed horizontally within a circle; it measures the parameters of a given world. The rho intersects the chi at its center and is placed vertically to represent theaxis mundi or world tree. The loop at the top of the rho represents the Supernal Sun at the summit of the world tree, from which all possibilities of creation proceed and to which they return. There can be no essential, but onl