When truth and tradition seem in opposition a personal choice may be forced upon anyone. Today's widespread discussions of urgent moral problems underline the relevance of these words from Meriol Trevor's conclusion to the first of the series of essays on her theme: in the light of the tensions released by the Second Vatican Council between two tendencies within the Church, the one towards uninhibited dialogue with the world at large, the other towards a prudent nurturing of traditional orthodoxy, Miss Trevor studies previous instances in the Church's history where this tension has been most in evidence. She recounts the great Modernist crisis at the beginning of this century (in which the English Jesuit Fr. Tyrrell was a leading light); the battle over Papal Infallibility leading up to the 1870 Definition; Lamennais' vain attempt to marry the Church to the liberal movement in the early nineteenth century, and earlier episodes to illustrate her theme-from which it is possible to trace the gradually widening rift between the Church and 'the World' which was scarcely evident before the sixteenth-century Council of Trent.