Objection 1. It would seem that prudence is not in subjects but only in their rulers. For the Philosopher says (Polit. iii, 2) that "prudence alone is the virtue proper to a ruler, while other virtues are common to subjects and rulers, and the prudence of the subject is not a virtue but a true opinion."
Objection 2. Further, it is stated in Polit. i, 5 that "a slave is not competent to take counsel." But prudence makes a man take good counsel (Ethic. vi, 5). Therefore prudence is not befitting slaves or subjects.
Objection 3. Further, prudence exercises command, as stated above (Article 8). But command is not in the competency of slaves or subjects but only of rulers. Therefore prudence is not in subjects but only in rulers.
On the contrary, The Philosopher says (Ethic. vi, 8) that there are two kinds of political prudence, one of which is "legislative" and belongs to rulers, while the other "retains the common name political," and is about "individual actions." Now it belongs also to subjects to perform these individual actions. Therefore prudence is not only in rulers but also in subjects.
I answer that, Prudence is in the reason. Now ruling and governing belong properly to the reason; and therefore it is proper to a man to reason and be prudent in so far as he has a share in ruling and governing. But it is evident that the subject as subject, and the slave as slave, are not competent to rule and govern, but rather to be ruled and governed. Therefore prudence is not the virtue of a slave as slave, nor of a subject as subject.
Since, however, every man, for as much as he is rational, has a share in ruling according to the judgment of reason, he is proportionately competent to have prudence. Wherefore it is manifest that prudence is in the ruler "after the manner of a mastercraft" (Ethic. vi, 8), but in the subjects, "after the manner of a handicraft."
Reply to Objection 1. The saying of the Philosopher is to be understood strictly, namely, that prudence is not the virtue of a subject as such.
Reply to Objection 2. A slave is not capable of taking counsel, in so far as he is a slave (for thus he is the instrument of his master), but he does take counsel in so far as he is a rational animal.
Reply to Objection 3. By prudence a man commands not only others, but also himself, in so far as the reason is said to command the lower powers.
Source: Summa Theologica (New Advent)