Hilary Armstrong changed the subject of ancient philosophy by devoting much of his long life to promoting the study of the Neoplatonist philosopher Plotinus. When Armstrong graduated from Cambridge University in 1932, Plotinus was widely regarded in the English speaking world as an obscurely mystical thinker, a minority interest at best, and certainly not a philosopher remotely comparable in intellect and rigour to Plato and Aristotle. Today, thanks to Armstrong's prolific output, especially his seven-volume text and translation of the Enneads, no serious scholar of ancient philosophy can afford to neglect Plotinus. As well as being a leading scholar of ancient philosophy, Armstrong was a devout, active, and increasingly idiosyncratic Christian; or perhaps better, a free-thinking Christian Platonist. His religious outlook consistently informed his view of Plotinus. As he grew older, he became increasingly ecumenical, critical of ecclesiastical hierarchy, and sympathetic to the religious experience of other faiths. He published extensively both on contemporary theological issues and also on early Christian thought and its relation to Greek philosophy, especially Platonism.
