The Visuddhimagga is the reason Theravada meditation instruction is as specific as it is. Buddhaghosa, working in fifth-century Sri Lanka, organised the whole path under ethics, concentration and wisdom: forty meditation objects with guidance on which temperament suits which, the jhanas mapped in sequence, and the stages of insight laid out in an order practitioners still recognise. It became authoritative to the point of being treated as a filter through which the canon is read — and the twentieth-century Burmese vipassana revival, which produced most of what the West calls insight meditation, is a partial argument with it about whether the jhanas are required at all.