Why Aquinas Would Agree That Human Economic Behaviour Is Largely Predictable
Authors: Conrad Richard , Hunter Peter 
Published: November 2019

Many people, from retailers and advertisers to the Chancellor of the Exchequer, work on the assumption that human economic behaviour is to a fair degree predictable, at least statistically. This paper asks how far the thirteenth-century Thomas Aquinas would agree that human behaviour (including economic behaviour) is predictable, both the behaviour of individuals and the behaviour of groups, and on what grounds. In doing so it also asks how any elements of predictability would square with Aquinas’ conviction that human beings enjoy liberum arbitrium, “free decision”. In the context of the present volume, exploring Aquinas’ position may promote a nuanced and multivalent approach to the question of what causes human behaviour, and liberate us from the fear that if human behaviour is caused, it cannot be free.

Aquinas was aware of the extreme complexity of the human psyche and of the organic interactions among its components. In particular, liberum arbitrium is achieved in interaction between intellect and will. The human will is the rational appetite, the ability to be attracted by the good perceived by reason. Any predictability of behaviour is therefore not a statistical result of intrinsic arbitrary randomness, as if acts of will were a kind of mental coin-flipping. Truly free behaviour is rationally explicable in terms of the goals it is right for human beings to pursue; final causality operates, in a way appropriate to responsible agents.

In an ideal world, not marred by sin, this would make human nature predictable to a limited degree. People would behave sensibly, as individuals and as communities, avoiding anything harmful. But people naturally differ in talents and temperament; geographical and historical circumstances vary; and human thinking is open-ended – within the time available, we can examine a situation from different points of view. In an unfallen world, people would happily adopt different social roles, and leaders’ decisions about how to apply the Natural Law to particular circumstances would be sensible, but also “prudential” as not determined by a rigid reasoning process such as geometry uses. Within a context of good citizenship, people would make varying choices about practical matters, to the extent that an unfallen race would be more interesting and vital – because more human – than a fallen one.

Our world is not ideal. The basic dynamics of intellect, will and emotions remain good, but individual temperaments can include propensities to vice as well as to virtue. Intellect and will are in important ways blank slates at birth, and embedded in a biological and social context. In the long growth towards moral maturity people are vulnerable to corrupt customs which can obscure even obvious points of the Natural Law. Though God’s grace is operative, not many people achieve the full moral freedom of an integrity in which emotions enhance a rational behaviour personally owned. When people do build up virtue, and thereby are partially liberated from the effects of the Fall, it becomes possible to predict in a general way that they will behave virtuously. But the open-endedness of thinking means that virtuous people will make varying choices about practical matters, more interesting and various than the dull and sadly predictable behaviour of people tied to various vices.

Since thorough-going vice is unnatural, most people tend towards a mediocre, partial moral consistency and behave rationally enough, obeying laws that carry sanctions, and listening to the more persuasive good advice; this will result in a certain predictability of behaviour on the part of the majority. They will also tend to follow bad laws and false persuasion without adequate reflection. Further, the failure to develop full rational control of their emotions (a control that must be “political” rather than “despotic”) leaves people vulnerable to emotional drives: in the here-and-now they often perceive lesser, but easy and immediate, goods as preferable to greater goods that they know are better, but which are more demanding and distant. At the personal level, individual temperaments lead to a certain predictability of behaviour; at the social level, predictability may result from the proportion of temperaments that is statistically likely. Aquinas saw these temperaments as due to inheritance and astrological influences; we would replace astrological explanations by genetic ones and a better understanding of children’s psychological development in its social context. For Aquinas, astrological influences remained potent throughout life, influencing the will indirectly, through the imagination and humours. We reject that form of predictability, but psychological experiments show that subconscious environmental factors, as well as fashion and peer-pressure, are potent. Aquinas also saw good and bad angels as influencing the human imagination and humours. Whether or not we agree with him on that, we recognise elements of unpredictability in social behaviour that are due to our vulnerability to unexpected mass movements, mass movements that we are inclined to label “demonic” – though there can also be good (“angelic”) mass-movements.

In conclusion: Aquinas would agree that human behaviour is predictable in some degree, but his perceptive pre-modern understanding of human psychology invites us to reflect afresh on the nature of freedom and on the forms and causes of predictability.