While histories of literature and philosophy have till now presented Calcidius as if he were no more than a secondhand mediator of Platonic thought, Peter Dronke, in The Spell of Calcidius, shows that this judgement must be radically revised. Calcidius’ commentary (probably of the early fourth century) on Plato’s Timaeus is a deeply individual work, which was able to inspire a fresh way of looking for truth, of searching for a world-picture that was not ready-made, among exceptional thinkers across eight centuries. The spell Calcidius cast was intellectual freedom, a Christian’s refusal to make Christian propaganda, a spirit of open enquiry. After the discussion of some key cosmological motifs in Calcidius himself and in Boethius, there follow chapters on the brilliant transformations of Calcidian thought in the ninth century by Eriugena and others; on the odi et amo towards Calcidius of Manegold of Lautenbach in the eleventh century; and on the ardent assimilation of his thought in the early twelfth by «us who love Plato», as William of Conches proclaimed. The final chapter shows how in Bernardus Silvestris’ epic, the Cosmographia (1147/8), the daring uses of language and speculation begun by Calcidius find their culminating creative renewal.