In an interview on NPR's Freakonomics (episode 258), economist Steven Levitt says, “I always just thought of demand curves as something that exist, like buildings or trees. They have a sort of a physicality to them.” At some point, the idea dawned on him that the demand curve was not real but “an artificial construct, which turns out to be incredibly valuable for organizing the world and knowing how to analyze problems … But I wanted to touch one; I wanted to hold a demand curve.…”

For Bernard Lonergan, Levitt's identification of existence with physical things is a common mistake, a “naive realism” that fails to recognize that many parts of reality, such as gravity, friendship, or grace, are not physical. Although these things cannot be seen, touched, or tasted, they are real and can be known—not through sense data but in the more general data of our consciousness. In Lonergan's terms, one might say Levitt needs an “intellectual conversion,” that is, the self-awareness that his knowledge is a combined product of paying attention to experience (both inner and outer), of questioning that experience, relating, or patterning the date of experience into an idea or hypothesis, and judging the idea as true insofar as it is verified by experience (again, both outer and inner, with the latter exemplified by the feelings attended to in Ignatian discernment).

David Hammond's recent book, Lonergan and the Theology of the Future: An Invitation, seeks to show how intellectual conversion could help theologians to better understand and appraise the historical development of doctrine as well as better to develop church doctrine in relation with a variety of cultures. The book begins with an accessible account of Lonergan's theory of knowing, including, for example, how theologians make use of reason and scientists rely on belief. Hammond discusses how knowledge can lead to conversion and how individual conversions can lead to shared religious practice and a communal quest to understand religion through the development of theology. Of particular importance is Lonergan's view that authentic theologians must be able to operate in both the imprecise but indispensable realm of common sense with its evocative, symbolic narratives as well as the abstract, systematic attempts of theory to answer questions about these narratives and their application to our lives. Hammond considers, in various chapters, how church doctrine has developed as a series of answers to questions and debates raised by the Bible: Is Jesus divine? Is he also human? How is Jesus related to the Father and the Holy Spirit? What is God's relation to human freedom and sin? What is the church's role?

Hammond shows how Lonergan's method can help theologians critically assess various competing answers, both ancient and modern. For example, Arius’ subordinationist position is traced to his “thinking in pictures … of God's status atop the Hellenistic hierarchy of being.” Similarly, Apollinaris thought Jesus could not be fully human because he imagined that in Jesus “the divine mind … replaced the human mind.” Lonergan's theoretical tools help theologians to avoid the twin temptations of relativism and rigid traditionalism, and thereby enable them to hand on church doctrines in a way that remains continuous with the past but can be adapted to different cultures and concerns.

Hammond has digested a large body of Lonergan's work well and produced a very readable book, best suited in my opinion to relative beginners who are believers and have some philosophical interest. Seminarians or first-semester graduate students would be ideal, but I would also recommend it to advanced undergraduate students and smart church-goers. The chapter topics are ordered well, and the writing is pedagogical in that it anticipates questions and provides good examples, such as the conversion of C. P. Ellis, a former member of the Ku Klan Klan. My main criticism is that, given the title, the book provides few concrete examples of how Lonergan advanced theology and how his students continue to do so. At times, the book is a bit bogged down by Lonerganian jargon, including when terms such as “authentic subjectivity” or “empirical residue” are not explained on first mention. I wish it had discussed Augustine on the psychological analogy and included an index, which is helpful for beginners.