St. Thomas discusses cases in which one should not follow the law:

As stated above (Article 4), every law is directed to the common weal of men, and derives the force and nature of law accordingly. Hence the jurist says [Pandect. Justin. lib. i, ff., tit. 3, De Leg. et Senat.]: “By no reason of law, or favor of equity, is it allowable for us to interpret harshly, and render burdensome, those useful measures which have been enacted for the welfare of man.” Now it happens often that the observance of some point of law conduces to the common weal in the majority of instances, and yet, in some cases, is very hurtful. Since then the lawgiver cannot have in view every single case, he shapes the law according to what happens most frequently, by directing his attention to the common good. Wherefore if a case arise wherein the observance of that law would be hurtful to the general welfare, it should not be observed. For instance, suppose that in a besieged city it be an established law that the gates of the city are to be kept closed, this is good for public welfare as a general rule: but, it were to happen that the enemy are in pursuit of certain citizens, who are defenders of the city, it would be a great loss to the city, if the gates were not opened to them: and so in that case the gates ought to be opened, contrary to the letter of the law, in order to maintain the common weal, which the lawgiver had in view.

He calls the attitude that leads one to set aside the law in such cases “epikeia,” or “equity,” which in this context means something like fairness or moderation:

As stated above (I-II:96:6), when we were treating of laws, since human actions, with which laws are concerned, are composed of contingent singulars and are innumerable in their diversity, it was not possible to lay down rules of law that would apply to every single case. Legislators in framing laws attend to what commonly happens: although if the law be applied to certain cases it will frustrate the equality of justice and be injurious to the common good, which the law has in view. Thus the law requires deposits to be restored, because in the majority of cases this is just. Yet it happens sometimes to be injurious—for instance, if a madman were to put his sword in deposit, and demand its delivery while in a state of madness, or if a man were to seek the return of his deposit in order to fight against his country. On these and like cases it is bad to follow the law, and it is good to set aside the letter of the law and to follow the dictates of justice and the common good. This is the object of “epikeia” which we call equity. Therefore it is evident that “epikeia” is a virtue.

“Fairness” is probably a good translation here, since someone who rigidly demands the application of the law in such a situation would often be called unfair in relation to the people involved.

Someone might object that much of the benefit of having a law directly depends on following it consistently, without making exceptions based on minute analysis of particular situations, as we saw in the last post. This is correct as far as it goes, but St. Thomas is not talking about analyzing each situation in detail and making an exception whenever there appears to be a benefit, but rather talking about situations which are extremely different from the situations considered by the law. Thus he says in the reply to the second objection:

He who follows the intention of the lawgiver, does not interpret the law simply; but in a case in which it is evident, by reason of the manifest harm, that the lawgiver intended otherwise. For if it be a matter of doubt, he must either act according to the letter of the law, or consult those in power.

To the degree that “laws of logic” can be analogously interpreted as rules for sensible thought and speech, telling one to behave in some ways and not in others, similar principles will apply. Thus, for example, an atheist confronted with the argument of Alexander Pruss for the existence of God based on the indeterminacy of language might not only be inclined to call it sophistical, but to add that it is an unfair way to argue. And indeed it is, precisely in the sense that it applies the rule “either say that A is B or say that A is not B” to situations for which it was not intended, namely situations where B is simply too vague to say. The rule is intended to make people think and speak sensibly, but Pruss is abusing the rule with the opposite result: that he does not speak and think sensibly.

Someone might agree that this is reasonable insofar as we are considering these laws as rules of behavior, but another issue comes up. Human laws are really intended to exclude some kinds of behavior that are really possible. And likewise, rules of logic are really intended to exclude some kinds of behavior that are really possible, e.g. making arguments like:

A: You always say I am wrong.

B: I said you were right about X.

A: See, you just said I was wrong again. You always say I am wrong!

I know from experience that this behavior is possible, and it does violate the laws of logic considered as rules of behavior. But someone might add that the laws of logic are also based on the nature of reality itself, and for this very reason we said that they are not conventions, but could not have been otherwise. So it seems to follow that it should be possible to expound the laws of logic in a form in which they are truly exceptionless, by expressing reality as it truly is.

There is some truth here, but there is also a problem analogous to a similar objection about human law. Consider the third objection and reply in the above article from St. Thomas:

Objection 3. Further, every wise man knows how to explain his intention by words. But those who framed the laws should be reckoned wise: for Wisdom says (Proverbs 8:15): “By Me kings reign, and lawgivers decree just things.” Therefore we should not judge of the intention of the lawgiver otherwise than by the words of the law.

…

Reply to Objection 3. No man is so wise as to be able to take account of every single case; wherefore he is not able sufficiently to express in words all those things that are suitable for the end he has in view. And even if a lawgiver were able to take all the cases into consideration, he ought not to mention them all, in order to avoid confusion: but should frame the law according to that which is of most common occurrence.

The objection here is similar. If there are cases where it wouldn’t be good to apply the law, the lawgiver ought to have enumerated those cases. St. Thomas replies that in reality you will not foresee every case, and that even if you could, enumerating them would simply cause confusion.

A similar thing applies if we consider the laws of logic. You can say, “If you say that A is B in an infinitely precise sense, and that B is C in an infinitely precise sense, you should also say that A is C,” and your claim might be exceptionless. The problem is that your claim has no cases: no one ever says anything in an infinitely precise sense.

And on the other hand, if you try to make your claim include some actual cases, you will not be able to avoid the possibility of exceptions, just as the human lawgiver does not foresee all cases. And as in the case of human law, if you attempt to enumerate all cases, you will simply cause confusion. Thus, for example, someone might say that the problem in the case of Queen Elizabeth is that we simply don’t have a precise enough definition for “old,” and they might then attempt to give a precise definition. But this would have several results:

1. First, the new word “old” would not have the same meaning as the original word, because the very fact that the original word is vague is part of what the word is. It is not accidental; it is not meant to have a precise cut-off.

2. Someone might attempt to remedy the above flaw by enumerating various circumstances, rather than giving a precise cut-off. “If you are less then 10 years old and you say that someone is ‘old,’ it signifies someone who is at least 15.” “If you are in your 30s and you say that someone is ‘old’, it signifies that they are at least 67.” And so on. But attempting to fix the first problem, you have simply compounded it. The new word still does not have the same meaning as the original word, because the original word was meant to be flexible; even your new rules have too much rigidity.

You could attempt to remedy the above problems by listing all the situations where people in fact use the word “old,” but that is not a definition: it is just an indefinitely long list. What St. Thomas said about human law, that it “ought not to mention them all,” is equally true about this situation. The point of defining “old” is to provide an explanation which is both general and flexible. Someone might argue that we should provide a list of all possible circumstances and what should be done in those circumstances, in order to avoid the flexibility of “epikeia,” but such an attempt would be absurd, and harmful to a good life. And it is equally absurd when we attempt to apply the same process to logic or to definitions, and harmful to sensible thought and speech.

What about reality itself? Isn’t it an exceptionless reality that a thing is what it is? Indeed. But this is neither a rule of behavior nor of speech. Nor is it a rule making something be some way; reality does not need something else to make sure that it turns out to be reality rather than something else. There is simply nothing else to be. Parmenides was right at least to this degree.