Stop people in the street, even a street in Oxford or St Andrews, and ask them to name a significant historical event we should commemorate in 2013: odds are you won’t hear about the 450th anniversary of the conclusion of the Council of Trent. Yet a fair number of our hypothetical victims will probably have heard of Trent, and many of those will have a view about its meaning and significance. Trent, they might say, inaugurated the Counter-Reformation, battening down the hatches on the closed, authoritarian and oppressive mind-set from which the Roman Catholic Church only (partially) managed to escape during the Second Vatican Council beginning in 1962 (coincidentally, last year’s forgotten anniversary). An alternative version, popular among some contemporary conservative Catholics, is that Trent eloquently codified the eternal truths that Vatican II proceeded carelessly to dilute. The current official line in Rome is that Catholic faith and morals, from the one council to the other and beyond, are to be interpreted through a ‘hermeneutic of continuity’; the world changes, the Church does not.

The very considerable achievement of John O’Malley, an immensely learned American Jesuit and academic, is twofold: he strips away these accumulated layers of myth to provide a balanced and convincing account of the Council in its proper historical