While I’ve had this book on my bookshelf for about 6 months, I haven’t taken the time to read through it until now. I would say this is the best introduction to deification/theosis around. It’s relatively short–124 pages of text–but it deftly covers both biblical and historical bases for this theology. In fact, I was quite impressed with the balanced presentation of biblical, patristic, catholic, orthodox, and protestant sources. This methodology works well to support his 3 theses: 1) deification is biblically grounded (i.e., it grew out of interpretation of biblical texts), 2) deification arose of patristic roots with branches in both the east and the west, and 3) deification is embedded with many other doctrines so that it should not be ignored nor should it trump other doctrines.
I think his interaction with key biblical texts was helpful and enlightening. In particular, he helped show the organic connection between key texts and later patristic interpretations, focusing on key themes like image, adoption, Second Adam, exchange, conformity to Christ, etc.
While this work is a volume in the Introductions to Catholic Doctrine series, Keating also did a good job of eliminating the polemics that can show up between catholics, othrodox and protestants. In fact, he shows that different traditions emphasise different aspects but that they maintain several key points. That is not to say that everyone teaches deification in the west, but that there are central catholic and protestant figures that use the terminology and they offer avenues for interaction for those in both traditions. Accordingly, he reclaims the significance for the west while critiquing some aspects.
Particularly important for his case are the rebuttals of particular charicatures of deification. These rebuttals are situated throughout the book, but he summarises them on page 122: deification is just an adoption of Greek philosophical ideas; deification is just based on Christ’s incarnation without proper emphasis on the cross, resurrection and ascension; and deification confuses the Creator and the created.
While he alludes to the anthropological effects that constitute deification (e.g., sanctification, 50-56 and cruciformity, 84-87), I thought this aspect of his discussion was quite thin with the only specific discussion (that I noted) on pages 111-13. To me the description of what actually happens, puts flesh on the bones and makes it clear what participation in the divine attributes really entails. Without this kind of discussion, it becomes a bit etherial, in my humble opinion. It can feel like semantic word games. I was surprised to see hardly any sustained discussion of the participation in immortality and incorruption. In my exposure to patristic texts, participation in these is the sine qua non of being deified.
In spite of this ommission, this text still serves as an excellent introduction for all faith traditions, and we would do well to consider his three main conclusions.