Conscience, said Newman, is ‘the aboriginal vicar of Christ’. For Vatican II, in Gaudium et Spes, it is ‘man's most secret core and sanctuary’. Neither image fits these Thomistic treatments nor what Thomas Aquinas said. Three of these treatments are by Dominicans: B.-H. Merkelbach (1871-1942), M.-M. Labourdette (1908-1990), and Réginald Beaudouin (1842-1907), at Louvain, Toulouse, and Le Saulchoir respectively. The fourth is by Matthew K. Minerd, compiler of the collection, self-identified as ‘a Ruthenian Catholic, husband and father’, at the Byzantine Catholic Seminary in Pittsburgh, Pennsylvania.

In the Summa Theologiae, Aquinas defines conscience as an act of judgment, deciding here and now that such-and-such is to be done because good, or avoided because evil, either of which courses of action would seem obviously right or wrong to a grown-up virtuous person (he assumes). Absent any full-on treatment of conscience in the Summa, the treatments here come not from Aquinas himself but from members of ‘the Thomist school’. Appearing in the Thomist Tradition series, the point is to save key texts from ‘the recent spate of anti-scholasticism’ (p.323). Prompted by whether one is obliged to follow an erroneous conscience (Summa Theologiae 1a 2ae 19, 5), to which Aquinas says yes, contrary to Franciscan contemporaries (p.125), a pile of books has accumulated since the late 16^th century under the arcane heading of ‘Probabilism’ — deciding which of the options for resolving problems of conscience is probably the right one.

Merkelbach finds it ‘dumbfounding’ and ‘a quite bizarre state of affairs’ that the moral theology textbooks in Catholic seminaries depart from Aquinas's lay-out in the Secunda Pars, centring on conscience, overlooking the role of prudence (pp.99-100). Beaudouin's Tractatus de conscientia, truly a rediscovery of a forgotten text, running from page 161 to page 320, deals at length with the rival ‘systems’ of managing problems of conscience. Merkelbach again, in an extract from his Summa theologiae moralis (5^th edition 1946), ‘arguably the best of all the Thomist manuals of the day’ (p.323), spells out how to deal with divided, anxious, or ill-informed consciences. In the opening eighty pages Dr Minerd provides a very lucid and unembarrassedly favourable overview of the great efforts of moralists in ‘the Thomist school’, such as Merkelbach and Beaudouin, to integrate this post-Tridentine focus on casuistry with Aquinas's prudence-centred ‘virtue ethics’. Against all this, Michel Labourdette's course notes insist that the casuistic approach to what is lawful and what is obligatory, is absolutely irreconcilable with Aquinas's ethics of beatitude, the human act, the virtues, practical reason, natural law, and grace.

It was all set off by the Commentaria (1577) of the Spanish Dominican Bartholomé de Medina (1528-1581). At its height, the controversy split partisans of ‘tutiorism’ (play safe, side with what you think is probably the most authoritative option) and those of ‘laxism’ (do what you feel is right) — famously mocked by Pascal, from a ‘rigorist’ Jansenist viewpoint. As the debate ramped up, the majority among moralists stood for ‘probabilism’ (where you see two probable, i.e., plausible reasons, one for and the other against your inclinations, do as you are inclined). Dominicans, by this time, subscribed to ‘probabiliorism’ (in cases of doubt accept the most authoritative advice, irrespective of what you feel). St Alphonsus Liguori, the great Redemptorist moralist of the post-Tridentine Church, came up with ‘equiprobabilism’ (faced with two conflicting and apparently equally well supported options you may lawfully take either).

Do post-Vatican II students dismiss all this because they are sunk by ‘the spate of anti-scholasticism’, as Dr Minerd says? A ‘mature Thomist’, he declares (p.76), cannot dismiss such a long debate in the Thomist school. In the same paragraph, however, he allows that he included Labourdette's notes precisely because he casts aside Beaudouin and Merkelbach as a ‘dead end’. Indeed, Réginald Garrigou-Lagrange (1877-1964), the most eminent Thomist of his day, shares this view — at least ‘somewhat’! And then, Servais Pinckaers (1925-2008), the most consulted Dominican moralist in recent times, is even ‘much more scathing about probabilism’ (p.76 fn 184).

Merkelbach's manual — ‘although more technical and hence more difficult’ (p.323) — is even better than that by Dominikus Prümmer (1866-1931). Prümmer's Vademecum was the standby in the English Dominican Province (in 1906 Prümmer actually taught moral theology at Hawkesyard). How to respond to penitents with ill-informed or scrupulous consciences, was treated in the pastoral formation of future confessors, but in a moral theology course which was a question-by-question reading of the Secunda Pars there was no occasion to discuss the probabilist theories. At Hawkesyard and Blackfriars, Oxford, the exponents of Aquinas's text were Antoninus-Dominic Finili (1889-1971), a committed Thomist trained at Fribourg, who mentioned Pinckaers with approval in 1960, citing his early article in Revue Thomiste (1955), the one (I think) about which Dr Minerd has reserves (p.56 fn 139); and Peter Worrall (1917-1968), whose doctoral thesis at the Angelicum is on Aquinas's knowledge of the early councils of the Church (Recherches de Théologie Ancienne et Médiévale 1956–7). Thomas Gilby, editor of the Blackfriars Summa, did Principles of Morality in the series (volume 18, 1966) and Prudence (volume 36, 1974), with a very useful appendix in the former on the so-called ‘moral systems’, and four excellent appendices in the latter, relating prudence to law, casuistry, conscience, and certainty, and maintaining that Aquinas's adherence to a pre-Tridentine devotional culture had no place for a problematic antithesis between a morality of obligation and an eudemian ethics of happiness (vol. 36, p. xvii).

Intriguingly, in connection with Aquinas on the human act (p.63 fn 153), Dr Minerd notes that he could have drawn on insights from G.E.M. Anscombe's Intention (1957); but this would have gone beyond his task here . Regrettably, then, we have no idea what he would have said. It is not clear whether he knows how much she studied Aquinas. In ‘Modern Moral Philosophy’, her seminal intervention (Philosophy 1958), against the mainstream in Oxford linguistic philosophy then, she proposes very provocatively that moral philosophers should jettison talk of obligation and duty (they no longer accepted the theological background, so she says). Instead, there needs to be a recovery of an Aristotelian account of action and intention, virtue, and human flourishing. She keeps quiet about Aquinas, not wanting to arouse prejudice. However, as an undergraduate at Oxford, she arranged one whole term on Aquinas with the Dominican, Victor White. She then embarked on a doctorate on Aquinas, supervised by Friedrich Waismann, which she gave up after a few years. Now, however, in the Routledge Philosophy Guidebook (2016) Rachel Wiseman refers to ‘the deeply Thomistic character of Intention, and of her philosophy more widely’ (p.18) — concluding, pithily and provocatively, with the claim that Anscombe's Intention is ‘a rendering of Aquinas's pre-Modern account for philosophy after the linguistic turn’ (p.175).

Jean Tonneau (1903-1991), explicating the Secunda Pars at Le Saulchoir in the early 1960s, has a splendid entry on ‘Devoir’ in the Dictionnaire de Spiritualité (1957). He starts from the lack of interest in ‘ought’ in Aquinas. As Anscombe sought to free modern English-speaking moral philosophy from the dominance of the concepts of duty and obligation, by reconstructing Aquinas's pre-Modern Aristotelian philosophical anthropology, so Dominican Thomists such as Tonneau, Labourdette, Pinckaers, and Gilby, set aside the same set of concepts in modern seminary textbooks, hoping to return to Aquinas's neo-Aristotelian ethics of happiness, virtue, and practical reason. Whether either Anscombe or these Dominicans succeeded in their parallel endeavours would take us too far here. In an equally intriguing footnote (p.iv), however, Dr Minerd, lists a clutch of recent books since The Emergence of Probability (1975) by Ian Hacking, in which he documents the new concern with certainty in mid 17^th century scientific discourse. Casuistic morality can seem ‘scientific’, thus very ‘modern’, as perhaps Beaudouin shows. Though obligation-centred morality and virtue ethics are surely irreconcilable, as Michel Labourdette says, Dr Minerd's collection of texts successfully brings these centuries of controversy among Dominican Thomists back to our attention.