The first full-scale study of an often-discussed but little understood heresy, the Alumbrados or 'Illuminated Ones', whose heterodox and sometimes extreme practices of mysticism and piety resulted in their suppression by the Spanish Inquisition.The first full-scale study of an often-discussed but little understood heresy, the Alumbrados or 'Illuminated Ones', whose heterodox and sometimes extreme practices of mysticism and piety resulted in their suppression by the Spanish Inquisition.