Morgan Llwyd (1619-1659), the nephew of a professional soldier and magician, was a Roundhead, a millenialist, a chaplain in the army of Oliver Cromwell, and later a civil servant of the commonwealth in Wales.

His Welsh-language writings, grounded in Puritan theology, yet enriched by his mysticism and esotericism, are considered masterpieces of imagery and cadence, among the best prose ever written in Welsh. His three English-language essays, first published in 1655 and collected here, display the depth and richness of his religious thought, and his passionate engagement in the...