Back in 1994, Stephen J. Pope in The Evolution of Altruism and the Ordering of Love cautiously advocated incorporating insights from behavioural biology into an Aristotelian/Thomistic account of human love. Pope observed how much twentieth century Catholic moral theology had either dispensed with the category of nature or reduced the role of nature in accounts of human agency. Not only did this represent a significant revision of Catholic moral theology, but it also left Catholic moral theologians with no common ground for engagement with the growing field of evolutionary ethics.
Since Pope's book we have witness something of a revival in the use of nature as a category in moral theology, but few works in moral theology have systematically incorporated insights from the behavioural sciences into a wider account of human agency. Ezra Sullivan's Habits and Holiness is a groundbreaking book, offering not only an account of how modern biopsychology can provide valuable insight into human behaviour, but doing so within a Thomistic theological account of human agency which is of great value in its own right.
The key to Sullivan's project is the centrality of habit for understanding human behaviour. I would be surprised if a survey of college courses introducing moral philosophy or theology today concluded that the study of habit plays a significant role. The revival of virtue ethics has not tended to elicit systematic reflection on the nature of habits and their general role in human behaviour, but Aquinas dedicates six questions in the Prima Secundae to habits in general before considering virtues as those habits which perfect human beings. Sullivan shows considerable scholarship in showing not only the central relevance of habit within the Summa Theologiae, but also how Aquinas uses the concept across his voluminous writings. This enables Sullivan to demonstrate how Aquinas uses the Latin term habitus in an analogous manner, ranging from the full sense of habit with voluntary human habits to various analogous senses in which other natural agents (animals, plants, inanimate objects) can be said to possess habits.
These analogies reflect the wider physical and metaphysical principles through which Aquinas brings out both the continuities and the discontinuities present in the natural world. Our reception of Aquinas is shaped by our historical context and in a world which either reduces human behaviour to the physical or opposes physical causality to human freedom, it can be difficult to appreciate how human behavior shares a common inheritance with wider physical nature, while at the same time human acts involve free choice between different ends. Sullivan brings out Aquinas's various analogous uses of habit to show how habits shape human behaviour at the various levels of the human being; according to our bodily, sensing, and rational being.
The insights Sullivan takes from biopsychology focus on the work of behavioural psychologists and are concerned with how human habits are shaped by a variety of factors, including physical dispositions to particular behaviours, developmental and environmental factors, and rational choices directing behavior to given ends. In an individual human being there is a complex interaction between these various levels of habit. In order to understand this interaction, we can distinguish between those habits which develop from our choices and those habits which we did not chose; the latter, however, should not be seen as necessarily contrary to human freedom.
To show how non-chosen habits are not only compatible with human freedom, but are required for the full exercise of our freedom, Sullivan draws upon Aquinas to distinguish acts and their related habits into four types: voluntary, imperfectly voluntary, nonvoluntary, and involuntary (p.116). Whereas the voluntary acts of a human being are acts which proceed from the will, and involuntary acts are acts contrary to the will, Sullivan (following Aquinas) defines nonvoluntary as acts that proceed form outside the person, but unlike involuntary acts do not contradict the person's will. Finally, imperfectly voluntary acts are acts which proceed from within the person, but they involve ‘sensory knowledge and natural estimation alone and without rational deliberation’ (p. 117). Sullivan argues that Aquinas categorizes nonvoluntary habits and imperfectly voluntary habits as ‘customary habits’, a term he also uses for the habits developed in non-rational animals through human training.
With these distinctions in place, Sullivan is in a position to investigate the development of human habits at the various levels of being covered by the analogous term habit. Nonvoluntary and imperfectly voluntary acts may incline us to act in ways contrary to our good, but when they do not they are necessary for human excellence. Habits are necessary for the development of our cognitive estimative abilities at the level of sense perception and the development of customary habits is essential for human flourishing: ‘the seemingly-automatic estimations of the cognitive power are key for a person acting according to reason’ (p.202). On the other hand, habits which have developed through voluntary acts can incline us to behaviours contrary to human flourishing and although we retrain our ability to act contrary to such vices Sullivan notes that: ‘We cannot with a single decision change our habits or their inclinations: the only way to move our sensory appetites is gradually to modify the judgments of our cognitive estimations by repeated acts’ (p. 201).
The above summary captures only part of Sullivan's project, and in addition to discussing the general nature of habit and virtue he also provides an excellent introduction to the theological virtues and the Gifts of the Holy Spirit, showing how Aquinas's understanding of habits is essential for his treatment of these theological topics, while adding insights from contemporary behavioural science. The book is intended, moreover, not only to help us understand human habits, but to show how insights from behavioural sciences applied within a Thomistic understanding of human agency can help us to shape our habits for our full flourishing. To this end chapter nine lays out steps for changing our habits (with a central role for merit), and chapter ten seeks to avoid the danger of behaviourist reductionism by integrating an account of habits with a wider account of the Christian life. This is a book which not only addresses a topic which is much neglected in moral theology but provides a wealth of material for the renewal of moral theology.
