Objection 1. It would seem that gnome (judging well according to general law) is not a special virtue distinct from synesis (judging well according to common law). For a man is said, in respect of synesis (judging well according to common law), to have good judgment. Now no man can be said to have good judgment, unless he judge aright in all things. Therefore synesis (judging well according to common law) extends to all matters of judgment, and consequently there is no other virtue of good judgment called gnome (judging well according to general law).
Objection 2. Further, judgment is midway between counsel and precept. Now there is only one virtue of good counsel, viz. euboulia (deliberating well) and only one virtue of good command, viz. prudence. Therefore there is only one virtue of good judgment, viz. synesis (judging well according to common law).
Objection 3. Further, rare occurrences wherein there is need to depart from the common law, seem for the most part to happen by chance, and with such things reason is not concerned, as stated in Phys. ii, 5. Now all the intellectual virtues depend on right reason. Therefore there is no intellectual virtue about such matters.
On the contrary, The Philosopher concludes (Ethic. vi, 11) that gnome (judging well according to general law) is a special virtue.
I answer that cognitive habits differ according to higher and lower principles: thus in speculative matters wisdom considers higher principles than science does, and consequently is distinguished from it; and so must it be also in practical matters. Now it is evident that what is beside the order of a lower principle or cause, is sometimes reducible to the order of a higher principle; thus monstrous births of animals are beside the order of the active seminal force, and yet they come under the order of a higher principle, namely, of a heavenly body, or higher still, of Divine Providence. Hence by considering the active seminal force one could not pronounce a sure judgment on such monstrosities, and yet this is possible if we consider Divine Providence.
Now it happens sometimes that something has to be done which is not covered by the common rules of actions, for instance in the case of the enemy of one's country, when it would be wrong to give him back his deposit, or in other similar cases. Hence it is necessary to judge of such matters according to higher principles than the common laws, according to which synesis (judging according to common law) judges: and corresponding to such higher principles it is necessary to have a higher virtue of judgment, which is called gnome (judging according to general law), and which denotes a certain discrimination in judgment.
Reply to Objection 1. Synesis (judging well according to common law) judges rightly about all actions that are covered by the common rules: but certain things have to be judged beside these common rules, as stated above.
Reply to Objection 2. Judgment about a thing should be formed from the proper principles thereof, whereas research is made by employing also common principles. Wherefore also in speculative matters, dialectics which aims at research proceeds from common principles; while demonstration which tends to judgment, proceeds from proper principles. Hence euboulia (deliberating well) to which the research of counsel belongs is one for all, but not so synesis (judging well according to common law) whose act is judicial. Command considers in all matters the one aspect of good, wherefore prudence also is only one.
Reply to Objection 3. It belongs to Divine Providence alone to consider all things that may happen beside the common course. On the other hand, among men, he who is most discerning can judge a greater number of such things by his reason: this belongs to gnome (judging well according to general law), which denotes a certain discrimination in judgment.
Source: Summa Theologica (New Advent)