Marcus Aurelius is best approximated as an INFP equivalent when his personality is interpreted through the typological framework of Chapter X of Carl Jung's Psychological Types. This conclusion requires an important qualification: Jung did not use the later four letter MBTI system, so INFP is not a literal Jungian designation. It is a modern shorthand for a Jungian configuration. In Marcus Aurelius, the strongest evidence points toward an introverted feeling type supported by intuition, rather than toward a thinking-dominant type. His philosophical writings are highly rational in expression, but their underlying psychological orientation is centered on an inwardly held system of values, conscience, meaning, and personal moral obligation. Jung defines introverted feeling as being determined principally by the subjective factor. Unlike extraverted feeling, it does not primarily adjust itself to external values or social expectations. Instead, it is concerned with an inner standard that evaluates the object according to an internally experienced value. Jung emphasizes that this feeling is often difficult to observe because it seldom appears directly on the surface. It can produce an outward appearance of reserve, indifference, or emotional restraint while possessing considerable inner intensity. This distinction is highly relevant to Marcus Aurelius. His Meditations are not primarily attempts to persuade an audience through emotional display. They are private reflections directed toward the regulation and purification of his own character. The recurring concern is not simply what society considers good, but what he himself must inwardly recognize as right and live according to. His reflections repeatedly return to questions of self-command, virtue, mortality, duty, resentment, desire, and the proper attitude toward external events. This inward moral orientation corresponds more closely to Jung's introverted feeling than to extraverted feeling. The fact that Marcus was an emperor does not automatically make him extraverted. Jung explicitly distinguishes psychological orientation from external circumstances. An introvert can occupy a highly public and powerful position while retaining a consciousness primarily oriented by subjective determinants. The decisive question is what governs psychological judgment, not how socially prominent the individual is. Jung states that introverted consciousness may be fully aware of external conditions while selecting subjective determinants as decisive. Marcus Aurelius provides a particularly strong historical example of this distinction. His position required him to deal constantly with armies, political institutions, administration, war, public duties, and interpersonal conflicts. Yet his philosophical reflections repeatedly attempt to detach his inner judgment from the immediate significance of these external circumstances. External events are treated as things that happen, while the individual's response to them is treated as the genuinely decisive matter. The emphasis is therefore placed on the subjective moral standpoint rather than on the object itself. His apparent emotional restraint should also not be confused with an absence of feeling. Jung specifically warns against interpreting introverted feeling types as people who have no feelings. Their feelings are intensive rather than extensive, developing in depth rather than being continually displayed outwardly. This description offers a useful way of understanding Marcus. His philosophical style is controlled and restrained, but the emotional and ethical intensity underneath it is considerable. His repeated concern with mortality, justice, human frailty, self-discipline, compassion, and the transience of worldly achievement indicates a powerful inner valuation rather than emotional emptiness. The N in the proposed INFP designation is best explained by intuition. Jung's model states that the auxiliary function differs in nature from the dominant function and serves it without becoming autonomous. He gives examples such as speculative thinking allied with intuition and philosophical intuition being systematized through intellect. In Marcus's case, intuition is a reasonable inference because his moral reflections continually move from immediate events toward broader symbolic and philosophical meanings. Individual experiences are interpreted as manifestations of larger principles concerning nature, mortality, human community, and the proper form of life. This intuitive element is important because Marcus does not merely react to individual events. He repeatedly abstracts from particular experiences toward general principles. An insult becomes an occasion to consider the nature of anger. Political power becomes an occasion to reflect on impermanence. Death becomes a means of examining the structure of human existence. Human conflict becomes a prompt to consider universal kinship and rational nature. The particular event is therefore subordinated to a larger internal vision of how life ought to be understood. The P designation should likewise be treated cautiously. Jung's original typology does not contain the MBTI distinction between Judging and Perceiving. Marcus was disciplined, organized, dutiful, and highly self-controlled, so a superficial application of MBTI stereotypes might favor a J designation. However, the four letter equivalent should not be derived from behavioral stereotypes. The more important Jungian structure is introverted feeling supported by intuition. Within the modern MBTI translation, that configuration is most closely represented by INFP. There is nevertheless a plausible alternative interpretation. Marcus was deeply committed to Stoic philosophical principles, and his writings frequently employ reasoning to discipline emotion and conduct. One could therefore argue for an introverted thinking type. However, Chapter X requires us to distinguish the instrument of expression from the dominant psychological criterion. Marcus uses reason extensively, but his reasoning repeatedly serves a prior evaluative concern: what is virtuous, what is within one's control, what attitude should one adopt, and what constitutes a good human life. The ultimate orientation is therefore more naturally interpreted as value-centered than as theory-centered. Consequently, INFP is the strongest four letter MBTI equivalent for Marcus Aurelius under the framework of Chapter X. The I reflects his inward psychological orientation, F reflects the primacy of an internally determined value system, N reflects his tendency to interpret concrete events through broader meanings and principles, and P represents the closest modern MBTI translation of the resulting configuration rather than a literal application of Jung's terminology. The deeper Jungian formulation is more important than the label itself: Marcus Aurelius resembles an introverted feeling type whose inner values are supported by intuitive perception. His historical role as emperor makes the contrast especially striking. Outwardly, Marcus occupied one of the most powerful positions in the Roman world. Psychologically, however, his surviving reflections repeatedly attempt to withdraw authority from external circumstances and return it to the inner standpoint of the individual. That movement from object toward subjective value is precisely the distinction that makes the introverted feeling interpretation particularly compelling within Chapter X.