Ezra SULLIVAN, OP, Habits & Holiness: Ethics, Theology, and Biopsychology. Washington, D.C.: The Catholic University of America Press, 2021, pp. 575. $34.95 pb. ISBN 978-0813233291. Reviewed by Wilburn T. STANCIL, Rockhurst University, Kansas City, MO 64110.

“Habit is what makes a human into a saint or sinner.”  With this opening line, Ezra Sullivan, professor invitato of theology and psychology at the Angelicum in Rome, launches the reader on a fascinating journey of habituation to virtue or vice. This journey brings together the disciplines of theology, philosophy, and biology. Though the book works primarily within a Thomistic framework, Sullivan includes useful suggestions for developing good habits and divesting ourselves of bad ones.

Sullivan begins with a discussion of the many possible ways the word “habit” can be used—from mechanical instincts to a disposition of the soul. He then explores how habits are necessary for understanding human behavior. After chapters on “subterranean” habits, that is, those that are involuntary, such as dispositions from human nature in general and those that are particular to each individual, Sullivan delves into the matter of human freedom as it relates to our capacity to shape our habits. From a Thomistic perspective, a fully voluntary action must engage the mind.  Even involuntary habits do not impede free choice and intentionality. As Aquinas writes, “when we act repeatedly according to reason, a modification is impressed in the appetite by the power of reason” (p. 205). Sullivan sees a similarity between Aquinas’ focus on reason and behaviorist psychology, which emphasizes a “habit loop,” composed of a cue/trigger, a behavior, and a reward, as a tool to help the individual judge and act according to reason.

In twin chapters on positive and negative habits and virtues, Sullivan first explores the four classical Cardinal Virtues: Prudence, Justice, Fortitude, and Temperance. He then tackles the thorny issue of how negative habits and vices develop. While strongly stressing that bad actions and habits are chosen, he does acknowledge the influence of personality disorders, chemical imbalances, and genetic predispositions. For example, negative behavior and habits can arise from biological factors, such as PTSD. However, he believes that the grounds for some mental disorders are often “shifting and uncertain” (p. 285).

Ultimately, Sullivan believes, even the effort to overcome involuntary negative habits requires more than reason.  Only grace can help.  Arguing that because of original sin we cannot achieve natural virtue in this life, Sullivan draws from Aquinas’ theology of supernatural grace.  Full, human flourishing cannot exist without the grace of God.  Grace completes and perfects nature. Sullivan develops this theme around the infused Theological Virtues (Faith, Hope, and Charity) and the Gifts of the Holy Spirit (Isaiah 11:2-3, Vulgate).

The final chapters center on practical suggestions for developing good habits and getting rid of bad ones. Habit change begins with self-knowledge but must include such things as identifying the behavior and the habit that produces it, the reward for performing the behavior, and a cue that will initiate the behavior. However, in order to form habits for life, Sullivan believes that the “infused habits open the door and form all other habits” (p. 473).

A strength of Habits & Holiness is its exposition of Aquinas’ understanding of habitus in his moral theology. The heavy focus on Aquinas is not surprising, since the book is a part of the Thomistic Ressourcement Series from The Catholic University of America Press. While the author does acknowledge that some of Aquinas’ views need to be corrected or at least refined, he points to many ways in which Aquinas’ theology is congruent with modern understandings of habit formation. Additionally, Habits & Holiness is an important book as an example of how theology and science can mutually enrich each other. Throughout the book, Sullivan is alert to ways in which neuroscience helps us understand human behavior and habit formation.

This growing interest in the relationship between human behavior, theology, and neuroscience is to be welcomed. As persons created of body and soul, there is a physiological basis for spirituality and ethical behavior. Habits and Holiness explores that relationship from the Roman Catholic tradition, and I strongly recommend Sullivan’s work. For Protestantism, a similar work I would recommend is that of Episcopal priest Bryan Spoon, Neuroscience and the Fruit of the Spirit. Spoon shows how spiritual practices can literally reshape the brain, leading to health and wholeness. Both books deserve a place on the bookshelf.