Obj. 3:  Further, as the moral virtues perfect the appetitive part of the soul, so do the intellectual virtues perfect the intellective part.  But the intellectual virtues are not mutually connected:  since we may have one science, without having another.  Neither, therefore, are the moral virtues connected with one another.

Obj. 4:  Further, if the moral virtues are mutually connected, this can only be because they are united together in prudence.  But this does not suffice to connect the moral virtues together.  For, seemingly, one may be prudent about things to be done in relation to one virtue, without being prudent in those that concern another virtue:  even as one may have the art of making certain things, without the art of making certain others.  Now prudence is right reason about things to be done.  Therefore the moral virtues are not necessarily connected with one another.

On the contrary, Ambrose says on Luke 6:20:  “The virtues are connected and linked together, so that whoever has one, is seen to have several”:  and Augustine says (De Trin. vi, 4) that “the virtues that reside in the human mind are quite inseparable from one another”:  and Gregory says (Moral. xxii, 1) that “one virtue without the other is either of no account whatever, or very imperfect”:  and Cicero says (Quaest.  Tusc. ii):  “If you confess to not having one particular virtue, it must needs be that you have none at all.”

I answer that, 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, but are not prompt in doing deeds of chastity.

But the perfect moral virtue is a habit that inclines us to do a good deed well; and if we take moral virtues in this way, we must say that they are connected, as nearly as all are agreed in saying.  For this two reasons are given, corresponding to the different ways of assigning the distinction of the cardinal virtues.  For, as we stated above (Q. 61, AA. 3, 4), some distinguish them according to certain general properties of the virtues:  for instance, by saying that discretion belongs to prudence, rectitude to justice, moderation to temperance, and strength of mind to fortitude, in whatever matter we consider these properties to be.  In this way the reason for the connection is evident:  for strength of mind is not commended as virtuous, if it be without moderation or rectitude or discretion:  and so forth.  This, too, is the reason assigned for the connection by Gregory, who says (Moral. xxii, 1) that “a virtue cannot be perfect” as a virtue, “if isolated from the others:  for there can be no true prudence without temperance, justice and fortitude”:  and he continues to speak in like manner of the other virtues (cf.  Q. 61, A. 4, Obj. 1).  Augustine also gives the same reason (De Trin. vi, 4).