For a long time it was common for Thomists to write commentaries on the Summa Theologiae. Cajetan, for example, wrote a multi-volume commentary on the whole of the Summa Theologiae (1507-1522), John of St. Thomas produced another (1637-1667) and in the twentieth century Garrigou-Lagrange authored several shorter books on a number of the main parts and sections of the Summa Theologiae. By and large such commentaries had two purposes; they expounded St Thomas's thought, and they expressed authorial developments of that thought. Unfortunately those authorial developments were not always precisely distinguished from St Thomas's thought. As a result as historical scholarship matured in the twentieth century and the distinction between St Thomas's thought and that of his commentators became progressively more important studies became more tightly focused on particular elements of St Thomas's thought and the practice of writing commentaries on the Summa Theologiae largely died out. In this book, however, J. Budziszewski returns to the practice and in a sequel to his earlier commentary on the questions on law in the Summa Theologiae (1a 2ae Qq. 90–97) now focuses his attention on the questions on happiness in the Prima Secundae.

The commentary follows the order of the first five questions of the Prima Secundae. Their major division is between the ultimate end of creatures considered as such (Q.1) and the specific candidate Aquinas proposes as the ultimate end of human beings, happiness (Qq. 2–5). The questions on happiness are then further subdivided according to what happiness is not (Q. 2), what happiness is (Q. 3), what conditions are required for happiness (Q.4), and how human beings can become happy (Q.5). Budziszewski devotes a section of his commentary (it is not divided into chapters) to each question and each question is further subdivided into sections corresponding to each article. Budziszewski takes each element of every article – objections, sed contra, corpus, and replies – and provides both the Blackfriars translation of those elements together with his own paraphrase in parallel text, as well as a commentary on each of those elements, before concluding each article with discussion(s) of key issues that arise.

The very size of the commentary, however, makes it difficult to do justice to it other than to say it is an impressive piece of work. Again and again the author is able to illuminate St. Thomas's ideas, to link them to correlative material in their historical sources, and to bring fresh light and insight to bear on familiar texts. One can dip into the commentary to focus on matters that pertain to one's particular interests or one can work one's way through all of it, perhaps in a classroom. Whichever approach is taken, the commentary will benefit a wide range of readers, both advanced and beginners alike.

Inevitably one can note some reservations. For instance in his commentary on Q.1 art. 1 corpus Budziszewski glosses human acts as ‘distinctive’ (p.15) of human nature. A little later in Q.1 art. 3 corpus, Budziszewski glosses proper motions as ‘characteristic of the kind of thing we have in mind’ (p. 40) giving as an example: ‘To fly is a proper movement of a bird’ (p. 41). But not only birds fly; insects do also, so do bats, and human actions are proper to human beings insofar as they are human (propriae hominis inquantum est homo). Consequently one is left to wonder whether the concepts Budziszewski employs have too great an extension. Surely what Aquinas meant is best captured by Aristotle's commensurate universal (Post. Analyt. 73b 26)? Human actions belong to all human beings and only to human beings. Proper motions belong to all members of a given kind and only to members of that kind.

Second, in his commentary on Q.1 art. 5, sed contra (pp. 70–71) ought Budziszewski not to have referred to the natural/supernatural ends of human beings debate in Thomism? Given Aquinas only excludes a human being from having several ultimate ends that are not ordered to each other (Ergo impossibile est esse plures ultimos fines unius hominis ad invicem non ordinatos) the path to two ordered ultimate ends, one natural the other supernatural, appears to have been left open. Surely such a possibility deserves some comment?

Third, Budziszewski's claim ‘To say that P constitutes the essence of Q is to say that it is the essence of Q … The soul constitutes the essence of the human being’ (p. 462) raises concern. It may be that there is some sense of ‘constitute’ which Aquinas employed that can be used to say the soul constitutes the essence of a human being. But the further claim that that which constitutes the essence of Q is the essence of Q would imply that the soul is the essence of a human being which is not a view Aquinas held, c.f. ST 1a Q.85 art. 1 ad 1.

Fourth, Budziszewski's discussion of Q.5 art. 4 ad 3, particularly his use of the water example – drinking water makes the drinker share the wetness of the water drunk, and his acceptance of the claim, ‘because someone shares in the vision of God, who is eternal, his vision is equally eternal’ (p.583) suggest a kind of transfer of divine attributes to the creature. This is problematic because if one can reason from the eternity of God to the eternity of the beatific vision ought one not also be able to reason from the omnipotence of God to the omnipotence of the beatific vision? Or likewise from the omniscience of God to the omniscience of the beatific vision? Yet Aquinas's point is more modest: that the beatific vision has no end follows as a consequence of the condition of the thing known, namely God, and since God satisfies all desire no soul would ever voluntarily turn aside from that vision. At no stage does any creature acquire any divine attribute.