In choosing a subject for this lecture, my mind turned to two books: both published during the war years, the first in 1941, Aldous Huxley's Grey Eminencel: the second at its very end, Arthur Koestler's The Yogi and the Commissar The titles of both have been incorporated into the language. The former was not its author's invention; but his use of it as the title of his study of Father Joseph won it a near universality of currency. So Lindemann is still spoken of as Churchill's scientific éminence grise. But the title of Koestler's essay, though less heard to-day, advertises dramatically a very important bifurcation of approach to the problems of human life and society, the one typified by the devotee in his ashram, the other by the commissar, the dedicated ‘social surgeon’ serving the cause of the total transformation of a given human society in the light of the directives of the party to which he belongs. But of course there is an important sense in which in Father Joseph, the subject of Huxley's book (which was incidentally a very well researched piece of work), the two life-styles are to a considerable extent conjoined. Father Joseph is at one and the same time the devoted fanatical Capuchin, the father-founder of the Calvarian order of nuns and the skilled, ruthless agent of Richelieu's purposes. He was no yogi, still less a commissar, but a man whose spiritual teachings rate an admittedly short and critical reference in Bremond's famous history of 17th century French spirituality, and one who played an unquestionably important part in the diplomatic history of a period, wherein diplomacy might well be characterized as war carried on by other means.