Outcomes that occur with probability zero are more relevant, and more confounding, to what we do see than we often think they are. Take, for example, the absence of nuclear war during the Cold War era. One side argued from the absence of war that the Soviet government was a pacific regime, and the West could safely demilitarize Western Europe without fear of Soviet aggression. The other side argued that the absence of war resulted from deterrence: eliminate the deterrent and they predicted we’d observe Soviet aggression. Two diametrically opposed theories that predicted the same non-event. Was the absence of war due to intrinsic Soviet preferences for peace, or did the absence of war result from the deterrent threat that induced Soviet non-aggression in the teeth, as it were, of their desire to dominate Europe?

There are at least two areas of judicial review where, with less at stake than nuclear annihilation, commentators similarly take a non-event to provide evidence for intrinsic preferences, and ignore the outcome actually results from deterrence.

As a first example, what to make of the centuries-long absence of congressional impeachments of judges for the political content of their actions? The late Chief Justice William Rehnquist, in his book, Grand Inquests: The Historic Impeachments of Justice Samuel Chase and President Andrew Johnson, argued that the acquittal of Chase in the Senate created a precedent that judges would not be disciplined by Congress “for their judicial opinions” and so resulted in “safeguarding the independence of that body.” Rehnquist’s theory is one about congressional preferences. The failure of the Senate to convict Chase changed congressional preferences permanently. Disciplining judges for their politics is now off the table, he argued.

Well, maybe.

The thing is, Rehnquist also noted in passing that political screeds by federal judges, which was the primary reason Chase was impeached, disappeared after Chase’s impeachment trial. Rather than suggesting that the Chase trial (and acquittal) set a congressional precedent that political judges not be impeached, we can turn the lesson around: Because of the deterrent effect of Congress’s action, loudmouthed federal judges learned to keep their mouths shut, or at least learned to sublimate their political opinions better than Chase did. In this latter reading Congress achieved its disciplinary goal without actually having to remove Chase from the bench. Peace has reigned since then not because congressional preferences changed, but because judges learned the lesson and were sufficient deterred from repeating Chase’s behavior. Both theories, the one about congressional preferences, the other about deterring improper judicial behavior, are consistent with the absence of judicial impeachments for political opinions since 1805. The “preference” theory is the conventional wisdom today, however.

A second example is the lesson we’re to draw from the fact that judges hardly ever strike down any legislation under the extremely deferential “rationality” standard in constitutional adjudication. In Gerald Gunther’s famous phrasing, deferential review is deferential in theory but “non-existent in fact.” Indeed, US courts, at both the state and Federal levels, rarely strike down legislation under the rationality standard.

To be sure, it could be that the rationality standard really has no bite at all. It could be an essentially nonexistent standard of review, one in which judges effectively give a pass to any and all legislation.

But I think there is an alternative theory, one in which the rationality standard has bite, and yet we would still predict that we only very rarely ever see a judge striking down actual legislation under the standard. The argument is that legislation that would fail the rationality standard would be so obviously unconstitutional that legislatures are deterred ever from enacting policies that would fail the standard (except perhaps by mistake). We of course would have no examples of the type of grossly factious legislation, at least not in modern times, because they’re deterred from enactment. Perhaps if we looked at frontier legislatures in the early 1800s, or city council actions through, say, the 1930s (or even later) we could observe relatively undisguised attempts at naked redistribution, the proverbial “robbing Peter to give to Paul.” Indeed, it was during the Jacksonian era that the early seeds of judicial commitment to class-neutral legislation were being planted in response to legislative abuses. In essence, this theory would go, the rationality standard deters the grossest forms of kleptocratic policies.

Again, however, two theories explaining something that happens only very rarely. Perhaps we so rarely observe judges striking down legislation under the rationality standard because the rationality standard is essentially a nonexistent standard of judicial review. Or perhaps we so rarely observe judges striking down legislation under the rationality standard because it is such a clear standard that it deters what it was created to deter, the basest sort legislative abuses. If the latter is correct, then even the deferential rationality standard has “bite,” its bite is simply unobserved because the policies it deters are never enacted in the first place.

To be sure, I don’t believe the Soviet regime was in fact pacific. I am, however, open to the conventional view of the evidence regarding judicial impeachments and rationality review. But I don’t believe the stylized empirical facts typically deployed as evidence for those views are really as strong as they are usually treated. Like the nuclear button never being pressed because the possibility of it being pressed structured behavior that we do see, judicial events that occur with a probability of zero can hugely effect the behavior that we do see.