Saint Thomas Aquinas identifies eight integral parts—or subvirtues—of the cardinal virtue of prudence. These integral parts are not optional or supplemental; rather, as integral, they are essential components that collectively constitute the fullness of prudence. In a Thomistic understanding, to possess a virtue like prudence means more than having a vague inclination toward wise decision-making—it requires the active presence and practice of all its constituent parts. If even one of these subvirtues is absent, the virtue of prudence is incomplete and, in effect, not truly present. Making prudent decisions without one component of prudence leaves us liable to error.
Here’s a helpful analogy: imagine a chair missing one of its legs. Most of the chair may still be intact, and it might resemble a fully functioning piece of furniture. Yet its stability, and therefore its utility, is compromised. So too with prudence—without all eight subvirtues, our moral and intellectual reasoning is unsteady and our judgments are prone to error.
The first of these subvirtues that we will put our minds to is memory, known in Latin as memoria.
What Is the Virtue of Memory?
Memory is not mere recollection of facts or past events, but rather a moral and intellectual habit of remembering rightly. Aquinas defines memory as the virtue by which one retains accurate and relevant knowledge about past experiences, particularly those related to human action and moral decision-making. One who possesses the virtue of memory is able to retain and apply not only the details of a given action but also its surrounding circumstances—understanding how it fits into the broader context of making a particular decision.
This virtue is deeply rooted in experience. As Aristotle explains in his Nicomachean Ethics (Book II, Chapter 1), the virtue we are referring to as memory “is engendered and fostered by experience and time.” Saint Thomas echoes this in the Summa Theologiae (II–II, Q. 49, A. 1), where he emphasizes that prudent judgment depends on one’s ability to recall past events accurately: “Memory of the past is necessary in order to take good counsel for the future.” Without the virtue of memory, one cannot properly assess similar future situations or learn from previous mistakes. Therefore, memoria is foundational to prudence, grounding it in the lived realities and lessons of the past.
How to Cultivate the Virtue of Memory
Saint Thomas offers four practical methods to actively cultivate and strengthen this virtue. Each one corresponds to a key insight about how the human mind works—and how we can train it to retain what matters most.
- Form Vivid and Unusual Images
The first method involves forming suitable yet somewhat unusual images or illustrations of what we wish to remember. He writes:
“We should have a suitable yet somewhat unwonted illustration of [the thing to be remembered], since the unwonted strikes us more, and so makes a greater and stronger impression on the mind… Now the reason for the necessity of finding these illustrations or images is that simple and spiritual impressions easily slip from the mind, unless they be tied, as it were, to some corporeal image, because human knowledge has a greater hold on sensible objects.” (Summa Theologiae, II–II, Q.49, A.1, ad 1)
Aquinas recognizes a basic psychological truth: we are more likely to remember something if it is connected to a vivid, concrete image—especially one that is unusual or striking. Because the human intellect operates in close union with the senses, abstract ideas or spiritual truths often need to be “anchored” in sensible realities in order to be retained.
For example, suppose someone wants to remember the importance of humility in leadership. Rather than simply repeating the abstract concept, they might form a mental image of a powerful king kneeling to wash the feet of a beggar. This vivid and somewhat unexpected image fuses spiritual meaning with a sensory impression, making it far more memorable than a mere definition.
By employing such unusual but fitting images, we train our minds to retain deeper truths, aiding not only memory but the broader exercise of prudence in our life.
- Organize Your Thoughts Carefully
The second way to cultivate the virtue of memory, according to Saint Thomas, is through order and careful consideration. He writes:
“A man should carefully consider and set in order the things he desires to remember, so that he may pass easily from one memory to another.” (Summa Theologiae, II–II, Q.49, A.1, ad 1)
Here, Saint Thomas emphasizes the importance of mental organization. Memory is not merely about retention but also about retrieval. When ideas or experiences are logically arranged and deliberately reflected upon, the mind is better able to move from one thought to the next in a coherent and connected way. Disorder, on the other hand, breeds forgetfulness and confusion.
For example, imagine a student of virtue—such as ourselves in these blogs—trying to remember the moral virtues. Rather than memorizing a disconnected list, the student organizes them under their cardinal categories—prudence, justice, fortitude, and temperance—and then groups the related subvirtues beneath each. By arranging the information in a meaningful structure, the student creates mental pathways that make recall more natural and intuitive.
This method is not just about academic memory—it applies directly to prudence. When we organize past experiences and moral principles in a structured way, we are more likely to recall and apply them effectively in future situations, thereby acting with greater wisdom and foresight.
- Be Earnest and Intentional
The third way to foster the virtue of memory, according to Saint Thomas, is by fostering earnest attention and concern for what we wish to remember. He explains:
“We must be anxious and earnest about the things we wish to remember, because the more a thing is impressed on the mind, the less it is liable to slip out of it. Wherefore Tully [Cicero] says in his Rhetoric that anxiety preserves the figures of images entire.” (Summa Theologiae, II–II, Q.49, A.1, ad 1)
Aquinas points to a psychological principle: the more seriously we regard something—whether through emotional investment, intellectual engagement, or moral urgency—the more deeply it is impressed upon our memory. Superficial or indifferent engagement leads to forgetfulness, whereas attentiveness and concern engrave the memory more firmly.
For example, consider someone who has once narrowly avoided a serious car accident due to a moment of distracted driving. Because the experience was emotionally intense and personally significant, the memory is etched deeply into their mind. There are actually certain neurotransmitters released in the brain that aid this process of deep memory formation. From that moment on, they drive with greater caution, remembering the consequences of inattention. The vividness and importance of the experience make it nearly impossible to forget—precisely because they were earnest and anxious about its meaning.
In the moral and spiritual life, this means we should not treat truth or virtue casually. If we approach our faith, responsibilities, or moral lessons with seriousness and intentionality, we are more likely to remember them when it matters most—thus enabling prudent action.
- Practice Frequent Reflection
Finally, Saint Thomas Aquinas teaches that the memory is strengthened through frequent reflection on the things we wish to retain. He writes:
“We should often reflect on the things we wish to remember. Hence the Philosopher [Aristotle] says (De Memoria I) that reflection preserves memories, because, as he remarks (De Memoria II), custom is a second nature: wherefore when we reflect on a thing frequently, we quickly call it to mind, through passing from one thing to another by a kind of natural order.” (Summa Theologiae, II–II, Q.49, A.1, ad 1)
Aquinas is drawing on Aristotle’s insight that repetition creates familiarity, and familiarity forms habit. Just as physical actions become second nature through repeated practice, so too do thoughts and memories become more accessible through regular reflection. The more often we return to an idea, the more naturally it surfaces when needed, forming mental pathways that support prudent judgment.
For example, a person who frequently meditates on Holy Writ will find that its words come to mind readily in moments of difficulty or moral decision. A verse or teaching that has been reflected upon repeatedly becomes a guiding light, available not because it was memorized once, but because it has become internalized through habitual contemplation.
In this way, reflection not only preserves memory but also integrates it into our moral and spiritual lives. Through frequent review and meditation, our memory becomes trained to recall the right things at the right time—an essential aspect of prudence.
Conclusion
In conclusion, Saint Thomas presents memory not simply as a natural faculty, but as a moral virtue—an integral part of prudence that must be intentionally cultivated. It is through memory that we preserve and draw upon past experiences, moral lessons, and truths that inform wise and timely decisions. By forming vivid images, ordering our thoughts, engaging our attention, and practicing regular reflection, we train our memory to serve as a reliable guide for future action. This virtue allows us to recall not just facts, but the deeper significance of what we have lived and learned, enabling us to judge rightly in complex situations. In the moral life, memory is not about nostalgia or mental storage—it is a dynamic, virtuous habit that connects our past to our present responsibilities, and helps orient our actions toward what is good and true. In cultivating memory, we take a necessary step toward becoming truly prudent and morally mature persons.
In our next post, we’ll take a closer look at the next part (or subvirtue) of prudence and explore how it helps shape the life of a truly virtuous and prudent person.