Thomas Aquinas

A brilliant theologian and philosopher, Aquinas was a monk and a scholar and his writings have contributed to thinking on philosophy and ethics, as well as theology. This profile will concern his principle contributions to ethics in natural law, conscience, virtue theory and proportionalism (as found in his Just War Theory).

One of Aquinas’ legacies is in his development of the natural moral law theory, through which he tried to construct an idea of what it was to be human. In this he was building on earlier ideas which dated back to Greek times which reflected an idea of a divine law over and above any human law which had to be respected. Aquinas’ understanding was that there was a concrete idea of what it was to be human and that this manifested itself in how people should live. He concluded that the governing principles of human law were to preserve your life (which had principle status), procreate, educate children, worship God and live in society. Moral actions (for Aquinas was a deontologist, believing that actions were intrinsically good or bad) were determined to be good depending on whether they were in accordance with one of these precepts. Critically, Aquinas  felt this Natural Law did not depend on knowledge of Holy Scripture but could be deduced through reason. This ethical thinking has largely informed Catholic Moral thought today, but it is not Aquinas’ only ethical contribution.

Aquinas’ thinking on conscience is also important. Aquinas argued that conscience is the power of reason. It is a device or faculty for distinguishing right from wrong rather than an inner knowledge of the kind suggested by other early Christian thinkers. He thought people tended towards goodness and away from evil (he called this the ‘synderesis rule’). Aquinas identified conscience as the power of reason for working out what was good and what was evil. At times people do bad things because they make an error in the process of discriminating good from ill. They pursue something which is apparently good but in fact is not truly good – their conscience has made a mistake. Consequently, a wrong done due to a faulty conscience is not morally blameworthy. He illustrates this with the curious example; if a man sleeps with another man’s wife thinking she was his wife, then he is not morally blameworthy because he was not free to do good.

Conscience is ‘reason making right decisions’ and not a voice giving us commands as suggested by the later Bishop Butler. Conscience deliberates between good and bad. Aquinas notes two dimensions of moral decision making, “Man’s reasoning is a kind of movement which begins with the understanding of certain things that are naturally known as immutable principles without investigation. It ends in the intellectual activity by which we make judgments on the basis of those principles…” (Summa Theologica, 1-1, Qu.79) synderesis is right reason, the awareness of the moral principle to do good and avoid evil. Conscientia distinguishes between right and wrong and also makes moral decisions.

Aquinas’ thinking on conscience provides a interesting background in which to place his natural moral law theory for it sheds more light on the process of moral decision making and the responsibility and the authority people have for their moral actions, properly deliberated upon, even if ultimately wrong. This sensitivity is expressed even more acutely in his thinking on the just war, in which he departed from absolute notions and cultivated a more proportionate understanding of the application of moral rules to a situation. In his thinking about war he drew on some of St Augustine’s statements and developed them further. He identified three necessary conditions for a just war: It had to be approved by an authorized authority which acts for the common good, as opposed to an illegitimate power acting for partial interests; for a just cause, rather than simple personal or national gain, “that those who are attacked, should be attacked because they deserve it on account of some fault”; and rightful intention uncorrupted by hidden motives. It must be for the furthering of some good or an avoidance of some evil.

Aquinas shows an acute sensitivity to politics which demonstrates, still in the current age, an ability to give explanations for war at the time which cloud true motivations. His moral thinking about war, like that of conscience, is concerned with inner motivations as well as outward actions. What is interesting is that it brings into the moral framework conditionality. If the criteria for justice are fulfilled the war is justified. The presence of these conditions or qualifications in both his thinking on war and conscience show the sensitivity that Aquinas knew was involved in moral decision making, which is sometimes lost when appeals are made to his teaching on natural law alone. Aquinas was also aware that moral behaviour was linked to character and he recalled in his writings the work of Aristotle on the virtues and vices. So in representing Aquinas’ ethical thinking it is important to take account of all his ethical work, rather than simply one component of it.