Despite different starting points, in the cloister and the world respectively, Anselm of Canterbury (1033-1109) and C. S. Lewis (1898–1963) enjoyed a mutual interest in the concept and experience of spiritual desire. Inspired by Lewis’ famous sermon, ‘The Weight of Glory’ (1941), but principally guided by Anselm’s reflections, this essay argues that desire exists in a dynamic relationship with love and that, as a journey of desire, the Christian life is extremely challenging, since it is a journey into mystery and towards moral perfection, but also contains and ultimately fulfils God’s promise of eternal joy. It is hoped that one by-product of this exploration may be to accord greater recognition to Anselm as a spiritual, even mystical, theologian, recognising him in Jean Leclercq’s description of an earlier monastic leader, Gregory the Great (d. 604), as a ‘doctor of desire’.