Philosophy of St. Thomas Aquinas: Three Determinants of Morality

Subject: Philosophy
Pages: 6
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Study level: PhD


It is rare to define good and evil without mentioning morality. In essence, goodness is termed as acting in accordance with the nature of doing things. However, such must be deemed to complete an individual’s fullness as a human being. On the other hand, evil is perceived as acts of doing against the will of God. In this context, a human being is unfulfilled and lacks goodness.

The three determinants of morality are notably the object, the end, and the circumstance (Aquinas, 2006). These determinants were coined by a classical philosopher known as Thomas Aquinas. The three determinants are essential in determining whether an individual’s action is good or evil.


The object refers to the act done by an individual. From this context, it is easy to understand the objectivity of human creation. From this perspective, an action can be deemed to be good or evil if it stands to be inconsistent or in conformity with the predetermined objectivity (Aquinas, 2006). An example of understanding this concept is through an act of murder. Murder is an action that involves taking or ending an innocent life. From this example, the act of murder is a wrong objective. On the other hand, the act of ending another life is not morally sound. In any case, murder has never been perceived as a good moral act. Under the eternal law, a human is made to believe that preservation of human life is a moral order, and actions contrary to that are morally wrong.

It should be noted that the determinant object, refers to what an individual is planning to commit in his or her immediate senses. Therefore, the goodness of an object is derived from what ought to be good. Basically, the result of an action does not amount to the object, but the action itself. This means that an action must first be willed by the doer of an action. For example, an individual must first be willing to take care of an ill patient. Eventually, the action of taking care of the patient becomes an object. Such an object will pass as a good deed.

According to Aquinas (2006), an action is comparable to a natural thing. For example, an action is deemed to have species from the object. On the other hand, a “form provides species to a natural thing” (Aquinas, 2006). Aquinas uses the example of a ball to define form (Aquinas, 2006). In this context, action is also defined by the object. Therefore, an action is determined to be good or evil.

Aquinas is very categorical that it is difficult to define the moral quality of an action. For example, taking a pen cannot be morally judged. However, if the action is described from an object perspective, then a moral judgment can be determined. For example, good action can be identified if taking the pen was for studying reasons. Therefore, an individual’s action must define an object with good morals (Aquinas, 2006). This means that mere action cannot be determined as good or moral unless an object is defined.

When an individual steal a chair, the act cannot be described as morally wrong. However, the act becomes morally wrong and evil when the individual decides to keep the stolen chair. The idea of keeping and possessing the stolen chair describes the object of the action.

As indicated earlier, the object is critical in determining actions. The object differentiates actions from another. Aquinas is of the view that each action must at least have a certain degree of goodness. This is derived from the idea that each action has a fullness of being. In case, there is a lack of fullness of being, then that action is considered evil.


Aquinas alleges that there are innate actions whose objects define the will (Aquinas, 2006). This means that the object of an innate action describes the end or the reason for the action. For example, if the action of studying was to become a doctor, then the end is defined by qualifying as a doctor. In this regard, it becomes clear that although all actions are voluntarily done by an individual, others are willed (Aquinas, 2006). In this context, two kinds of actions exist; interior and exterior action. Interior actions are willed and their objects become or are defined as the end (Aquinas, 2006; Aquinas, 1990). On the other hand, exterior actions are objectively perceived as mere actions. Basically, the end and the object are related from a natural perspective.

The influence of the end on an object is sometimes direct or indirect (Aquinas, 1990). The end is sometimes known to produce other multiple actions. For example, when someone works to earn money, the object of the action is money. However, another object is derived if earning that money was meant to be given to the less fortunate.

From the above example, the goodness of an object is determined by the end. However, goodness should not depend on another series of actions. For example, stealing money from the poor does not justify the end as morally good. The goodness of an object and action can be determined from the end of the initial action. If such is deemed to be of absolute goodness, then a measure of goodness is determined from the initial will and object (Aquinas, 1990). For example, if the action’s object was to steal money on behalf of the less fortunate and not for personal gains. As indicated earlier, such action and object do not pass as acts of absolute goodness. The second act of giving to the less fortunate becomes an act of absolute goodness since the act is in itself of absolute goodness (Aquinas, 1990).

According to Aquinas, it is possible for a person to indulge in good acts and achieve evil objects (Aquinas, 2006; Aquinas, 1990). On the other hand, a good object or intention can eventually influence evil acts to achieve a good end. From the principles of eternal law, it is the “obligation of an individual to conform all intentions towards absolute truth” (Aquinas, 2006). Human conscience distinguishes what is evil from good. Therefore, the conscience should act as guidance before the execution of any action.

Aquinas tries to demystify the statement “an evil act justifies a good intention” (Aquinas, 2006). This means that if the object or the end is evil, then the action is still perceived as evil. The absoluteness of goodness is a part of eternal law and cannot be compromised from a moral perspective.


Circumstances are perceived as conditions of certain actions. These circumstances are designated conditions under certain times and places. The circumstances have a certain degree of influence over the morality of actions (Aquinas, 2006; Aquinas, 1990). In this respect, the “circumstances can increase or decrease the degree of goodness or evil in specific actions” (Aquinas, 1990). However, evil actions do not change after being subjected to certain conditions. “Circumstances do not influence the making of an action but influences an action that already exists” (Aquinas, 2006). This means that the morality of an action is also determined by external factors. An example of such a circumstance is when one walks past a field that is restricted. In this scenario, the act of walking past the field has no moral obligation. The addition of a restrictive condition makes the act morally evil. Therefore, the act of walking pats the restricted field amounts to trespassing.

Another example of how a circumstance impacts the morality of an action is as follows. When an individual steals 5 dollars and another steals 10 dollars, the moral quality of the act remains the same. However, the act of stealing 5 dollars may be viewed as a lesser evil compared to stealing 10 dollars. Basically, stealing less amount of money lessens the repercussions that may befall the aggressor. In this respect, individuals are advised to take extra caution when executing actions under certain circumstances. Being prudent and conscious is called for among individuals as a matter of making sound judgments. Subjective culpability relies heavily on an individual’s conscious interpretation of natural law and objective truth. As indicated earlier, time and place can alter the moral tone under which an action was taken. An intelligent person would use wisdom and knowledge to solve a problem, even if it does not conform to natural law. If such a decision is deemed to be of benefit to the greater good, then the moral quality of the action is not lessened. Natural law acknowledges and appreciates that circumstances are additions that exist in form of accidents and shape the goodness of an object (Aquinas, 2006). However, an action can remain evil even after the prevalence of certain conditions.

Is there such a thing as intrinsically evil act by its object?

The concept of intrinsic evil was also coined by Thomas Aquinas. Aquinas’s perspective on evil is derived from the definition that evil is merely the absence of goodness (Aquinas, 2003). According to Aquinas (2003), intrinsic evil entails “actions that are opposed to the intent of God’s will” (Aquinas, 2003). Moreover, intrinsic evil limits the fulfillment of man as God’s creation. More importantly, Aquinas’s description of intrinsic evil is not linked with intentions. This means that they can only be analyzed from the perceptive of their object. Basically, intrinsic evil remains “morally wrong, even when they are conducted under certain conditions” (Aquinas, 2003). Intrinsic evils are never influenced by circumstances. In addition, the object of intrinsic evil can never change to goodness. In this context, the only alternative to such actions is choosing another action.

Intrinsic evil acts are beyond human understanding, control and directly contradict the purpose of man (Aquinas, 2003). This means that once such acts are committed, they can never be changed or altered. According to Aquinas (2003), an example of actions considered as intrinsic evil includes murder, fornication, lying and adultery. Other intrinsic evil acts include acts of homosexuality, blasphemy and human cloning. These evil acts portray a greater absence of perfection in a human being.


Aquinas, T. (1990). A summa of the summa: The essential philosophical passages of St. Thomas Aquinas’ summa theological. Ft. Collins, CO: Ignatius Press.

Aquinas, T. (2003). Aquinas: On evil C. Oxford, OX: Oxford University Press.

Aquinas, T. (2006). Summa theologiae index: Volume 61: General index. Cambridge, CB: Cambridge University Press.