"Moral virtue may be considered either as perfect or as imperfect. An imperfect moral virtue, temperance for instance, or fortitude, is nothing but an inclination in us to do some kind of good deed, whether such inclination be in us by nature or by habituation. If we take the moral virtues in this way, they are not connected: since we find men who, by natural temperament or by being accustomed, are prompt in doing deeds of liberality [(opera liberalitatis)], but are not prompt in doing deeds of chastity [(opera castitatis)]."
St. Thomas Aquinas, ST I-II.65.1.Resp., underscoring mine. See also ad 1: "if he exercise himself by good deeds in regard to one matter, but not in regard to another, for instance, by behaving well in matters of anger, but not in matters of concupiscence; he will indeed acquire a certain habit of restraining his anger; but this habit will lack the nature of virtue, through the absence of prudence, which is wanting in matters of concupiscence."
"Aquinas also identifies a fourth type of virtue, which Jean Porter does not discuss (to my knowledge). This is the infused virtue that is not connected with the others. Aquinas explains the possibility of possessing infused virtue in merely habitual or inchoate states (habituales formae). Although all the virtues are infused with charity, they are not necessarily exercised, as when there is an impediment . . . or as when one exhibits perfect faith but imperfect charity."
Craig Steven Titus, "Moral development and connecting the virtues: Aquinas, Porter, and the flawed saint," in Ressourcement Thomism: sacred doctrine, the sacraments, and the moral life: essays in honor of Romanus Cessario, O. P. (Baltimore: The Catholic University of America Press, 2010), 348 (330-352), underscoring mine.
Yet in one of the very passages Titus cites in support of this, Thomas says explicitly that "faith may be without charity, but not as a perfect virtue [(fides est quidem sine caritate, sed non perfecta virtus)]" (ST I-II.65.4.Resp.). So I need to follow up on those passages in De virtutibus cardinalibus.
In any case, this is an important response to Jean Porter's discussion of Martin Luther King Jr. in "Virtue and sin: the connection of the virtues and the case of the flawed saint," Journal of religion 74, no. 4 (1995): 521-539, the full complexities of which I won't attempt to reproduce here, but only these sentences from the Conclusion (351, italics mine):
for St. Thomas, charity (as a fledgling disposition [not yet a more or less established virtue confirmed in act]) neither guarantees its own full development or the connection of the other infused virtues nor guarantees a coherent psychological structure of the acquired virtues (as dispositions [not yet more or less established virtues confirmed in act]). Aquinas explains that in the exercise of infused moral virtues we can 'experience difficulty in their works, by reason of certain ordinary dispositions remaining from previous acts. This difficulty does not occur in respect of acquired moral virtue: because the repeated acts by which they are acquired remove also the contrary dispositions.'
For Aquinas there can be "an imperfect connection of charity and the other infused virtues" (350), as well as "growth" in or a falling away on the level of the acquired virtues (351). "A static point does not exist. At any moment, either a person advances toward a more coherent connection of these dispositions [infused and acquired], or he regresses" (351). From p. 352:
Aquinas's approach. . . . construes moral development as a process of habitualizing, connaturalizing, and connecting the virtues, while not losing hope for any 'flawed saint,' a term that Aquinas would not use. In particular, God can revive the person—after a grave sin—to repent, to seek forgiveness, and to repair (when possible) the damage done. The person thus returns to the pathway of development with renewed charity and infused virtue, which includes the possibility of further connecting the virtues, sanctifying desire, and even being disposed to martyrdom in a state of grace.
See also Eleanor Stump:
Considered in this way, courage can fail to be a moral disposition; and it can be had even by those who are not moral people.
Cf. St. John Chrysostom, Homily 15 on Matthew, as trans. NPNF: "there are many who show mercy, and who commit no rapine, nor are covetous, who yet are guilty of fornication and uncleanness [(πορνεύουσι δὲ και ἀσελγαίνουσι)] ; to signify that the former alone suffices not, He hath added this, much in the same sense as Paul, writing to the Corinthians, bore witness of the Macedonians, that they were rich not only in almsgiving, but also all other virtue" (Greek from Homiliae in Matthaevm, ed. Field (1836), vol. 1, p. 194).