It's a great pleasure to see the doctoral dissertation, defended in 1989, for which one served as a reader, finally appear in print, of course with extensive updating and addition, to keep up with current scholarship. Rocca's dissertation was certainly one of the best I have ever read, and one from which I have learned much, and the author has rendered the academic community a great service by making his work available to a wider readership.
Rocca intends his work to be an analytic, synthetic, and genetic study of Thomas's theological epistemology, that is, how humans come to know and speak of God who is acknowledged as the Incomprehensible Mystery. Three key concepts underlie this epistemology: negative theology, positive theology, and analogy. The task then is to show how these three elements interrelate and condition one another in Thomas's thought. This is easier said than done, since Thomas has not written a specific treatise on the subject as envisioned; rather he speaks more often of the knowledge of God and the predication of divine names and in scattered places. One of the merits of Rocca's work is to offer a close intertextual analysis and interpretation of all the pertinent passages in Thomas's work, both well known and lesser known.
The book is divided in four parts. The first introduces negative theology, especially as espoused by Pseudo-Dionysius and John Damascene and as interpreted by Thomas. Rocca highlights Thomas' teaching on the incomprehensibility of God and on his approach to God through the via negativa. The second part discusses analogy, first in Aristotle and then extensively in Thomas. Rocca emphasizes that for Thomas analogy does not lie in concept but in judgment, and that therefore his theological epistemology gives priority to truth over meaning. The third part singles out what Rocca calls "crucial truths" that Thomas upholds about God, in particular God's existence; God as creator, God as infinite, perfect, transcendent and immanent; and the creature's relationship to God. The last part discusses Thomas's positive theology by focusing on his theory of divine names and his key distinction between res significata and modus significandi.
Rocca summarizes Thomas's theological epistemology in a helpful statement: "Thomas weaves his negative and positive theology together, precisely because only that interweaving can do justice to the fact that the church must speak and praise, must invoke and love and follow the God who just is the Mysterious and Incomprehensible One who ever escapes and is never caught by our ideational and conceptual schemes" (xvii, 353). Rocca makes it clear that for Thomas truth enjoys primacy over meaning, truths of faith over truths of reasons, and "both-and" approach over "either/or" approach.
Despite the highly technical nature of the subject-matter, Rocca writes in an accessible and clear language. His work should be in every theological library. I also recommend it highly for a graduate seminar on Thomas and on theological epistemology.