Causation

Problems with the counterfactual test. Very generally there are four sorts of problems with the counterfactual test for causation in fact. One set of these problems has to do with proof and evidence. As an element of the prima facie case, causation-in-fact must be proven by the prosecution beyond a reasonable doubt. Yet counterfactuals by their nature are difficult to prove with that degree of certainty, for they require the fact finder to speculate what would have happened if the defendant had not done what he did. Suppose a defendant culpably destroys a life preserver on a seagoing tug. When a crewman falls overboard and drowns, was a necessary condition of his death the act of the defendant in destroying the life preserver? If the life preserver had been there, would anyone have thought to use it? Thrown it in time? Thrown it far enough? Have gotten near enough to the victim that he would have reached it? We often lack the kind of precise information that could verify whether the culpable act of the defendant made any difference in this way.

A second set of problems stems from an indeterminacy of meaning in the test, not from difficulties of factual verification. There is a great vagueness in counterfactual judgments. The vagueness lies in specifying the possible world in which we are to test the counterfactual (Moore, 1997, pp. 345–347). When we say, "but for the defendant's act of destroying the life preserver," what world are we imagining? We know we are to eliminate the defendant's act, but what are we to replace it with? A life preserver that was destroyed by the heavy seas (that themselves explain why the defendant couldn't destroy the life preserver)? A defendant who did not destroy the life preserver because he had already pushed the victim overboard when no one else was around to throw the life preserver to the victim? And so on. To make the counterfactual test determinate enough to yield one answer rather than another, we have to assume that we share an ability to specify a possible world that is "most similar" to our actual world, and that it is in this possible world that we ask our counterfactual question (Lewis, 1970).

The third and fourth sets of problems stem from the inability of the counterfactual test to match what for most of us are firm causal intuitions. The third set of problems arise because the counterfactual test seems too lenient in what it counts as a cause. The criticism is that the test is thus overinclusive. The fourth set of problems arise because the counterfactual test seems too stringent in what it counts as a cause. The criticism here is that the test is underinclusive.

The overinclusiveness of the test can be seen in at least four distinct areas. To begin with, the test fails to distinguish acts from omissions, in that both can be equally necessary to the happening of some event (Moore, 1993, pp. 267–278; Moore, 1999). Thus, on the counterfactual test both my stabbing the victim through the heart and your failure to prevent me (though you were half a world away at the time) are equally the cause of the victim's death. This is, to put it bluntly, preposterous.

It is important to see that there is a counterfactual question to ask about omissions before we blame someone for them. We do need to know, counterfactually, if the defendant had not omitted to do some action, whether that action would have prevented the harm in question. Yet the counterfactual test of causation would turn this question about an ability to prevent some harm, into a question of causing that which was not prevented. It is a significant objection to the counterfactual theory that it blurs this crucial distinction.

A second way in which the counterfactual test is overinclusive is with regard to coincidences. Suppose a defendant culpably delays his train at t₁; much, much later and much further down the track at t₂, the train is hit by a flood, resulting in damage and loss of life (Denny v. N.Y. Central R.R., 13 Gray (Mass.) 481 (1859)). Since but for the delay at t₁, there would have been no damage or loss of life at t₂, the counterfactual test yields the unwelcome result that the defendant's delaying caused the harm.

While such cases of overt coincidences are rare, they are the tip of the iceberg here. Innumerable remote conditions are necessary to the production of any event. Oxygen in the air over England, timber in Scotland, Henry the VIII's obesity, and Drake's perspicacity were all probably necessary for the defeat of the Spanish Armada (Moore, 1993, pp. 268–269), but we should be loath to say that each of these was equally the cause of that defeat.

A third area of overinclusiveness stems from the rockbed intuition that causation is asymmetrical with respect to time (Moore, 1999). My dynamite exploding at t₁ may cause your mother minks to kill their young at t₂, yet your mother minks killing their young at t₂ did not cause my dynamite to explode at t₁. The counterfactual test has a difficult time in accommodating this simple but stubborn intuition.

To see this, recall the logic of necessary and sufficient conditions. If event c is not only necessary for event e but also sufficient, then (of necessity) e is also necessary for c. In such a case c and e are symmetrically necessary conditions for each other and, on the counterfactual analysis, each is therefore the cause of the other. Intuitively we know that this is absurd, yet to avoid this result we must deny that some cause c is ever sufficient (as well as necessary) for some effect e. And the problem is that almost all proponents of the necessary condition test readily admit that every cause c is, if not sufficient by itself, then sufficient when conjoined with certain other conditions c' c", etc. (Mill, 1965, book 3, chap. 5, sec. 3). Sufficiency seems to well capture the commonsense view that causes make their effects inevitable. Yet, with such inevitability of effects from their causes come a necessity of those effects for those causes. Therefore, every effect is also a cause of its cause?

The fourth sort of overinclusiveness of the counterfactual analysis can be seen in cases of epiphenomena. One event is epiphenomenal to another event when both events are effects of a common cause (Moore, 1999). I jog in the morning with my dog. This has two effects: at t₂, my feet get tired; at t₃, my dog gets tired. Intuitively we know that my feet getting tired did not cause my dog to get tired. Yet the counterfactual analysis suggests just the opposite. My jogging in the morning was not only necessary for my feet getting tired, it (sometimes at least) was also sufficient. This means (see above) that my feet getting tired was necessary to my jogging in the morning. Yet we know (on the counterfactual analysis) that my jogging in the morning was necessary to my dog getting tired. Therefore, by the transitivity of "necessary," my feet getting tired was necessary to my dog getting tired. Therefore, the tiring of my feet did cause the tiring of my dog, contrary to our firm intuitions about epiphenomena.

The fourth set of problems for the counterfactual test has to do with the test's underinclusiveness. Such underinclusiveness can be seen in the well-known overdetermination cases (Moore, 1999; Wright, 1985, pp. 1775–1798), where each of two events c₁ and c₂ is independently sufficient for some third event e; logically, this entails that neither c₁ nor c₂ is necessary for e, and thus, on the counterfactual analysis of causation, neither can be the cause of e. Just about everybody rejects this conclusion, and so such cases pose a real problem for the counterfactual analysis.

There are two distinct kinds of overdetermination cases. The first are the concurrent-cause cases: two fires, two shotgun blasts, two noisy motorcycles, each are sufficient to burn, kill, or scare some victim. The defendant is responsible for only one fire, shot, or motorcycle. Yet his fire, shot, or noise joins the other one, and both simultaneously cause some single, individual harm. On the counterfactual analysis the defendant's fire, shot, or noise was not the cause of any harm because it was not necessary to the production of the harm—after all, the other fire, shot, or noise was by itself sufficient. Yet the same can be said about the second fire, shot, or noise. So, on the but-for test, neither was the cause! And this is absurd.

The preemptive kind of overdetermination cases are different. Here the two putative causes are not simultaneous but are temporally ordered. The defendant's fire arrives first and burns down the victim's building; the second fire arrives shortly thereafter, and would have been sufficient to have burned down the building, only there was no building to burn down. Here our intuitions are just as clear as in the concurrent overdetermination cases but they are different: the defendant's fire did cause the harm, and the second fire did not. Yet the counterfactual analysis again yields the counterintuitive implication that neither fire caused the harm because neither fire was necessary (each being sufficient) for the harm.

Situated rather nicely between these two sorts of overdetermination cases is what this author has called the asymmetrical overdetermination cases (Moore, 1999). Suppose the defendant nonmortally stabs the victim at the same time as another defendant mortally stabs the same victim; the victim dies of loss of blood, most of the blood gushing out of the mortal wound. Has the nonmortally wounding defendant caused the death of the victim? Not according to the counterfactual analysis: given the sufficiency of the mortal wound, the nonmortal wound was not necessary for, and thus not a cause of, death. This conclusion is contrary to common intuition as well as legal authority (People v. Lewis, 124 Cal. 551, 57 P. 470 (1899)).

Defenders of the counterfactual analysis are not bereft of replies to these objections. As to problems of proof they assert that counterfactuals are no harder to verify than other judgments applying causal laws to unobservable domains (such as those parts of the past for which there is no direct evidence, or those aspects of the universe too far removed for us to observe, or those future events beyond our likely existence). As to the problem of indeterminacy, they assert that we test counterfactuals in that possible world that is relatively close to our actual world; usually this means removing the defendant's action only, and then suspending enough causal laws so that events that normally cause such action just did not on this occasion (Wright, 1988). As to the problems of omissions and asymmetry through time, they assert that we should simply stipulate that a cause is not only a necessary condition for its effect, but it is also an event (not the absence of an event) that precedes (not succeeds) the event which is its effect. Such stipulations are embarrassingly ad hoc, but they do eliminate otherwise troublesome counterexamples. With regard to coincidences and epiphenomenal pairs of events, they assert that there are no causal laws connecting classes of such events with one another; one type of event is not necessary for another type of event, however necessary one particular event may be for its putative (coincidental or epiphenomerical) "effect." With regard to the embarrassment of riches in terms of how many conditions are necessary for any given event or state, they typically bite the bullet and admit that causation is a very nondiscriminating relation; however our usage of "cause" is more discriminating by building in pragmatic restrictions on when certain information is appropriately imparted to a given audience. As to the problem posed by the concurrent overdetermination cases, they usually urge that if one individuates the effect finely enough in such cases, one will see that each concurrent cause is necessary to that specific effect (American Law Institute, 1985). A two-bullet death is different than a one-bullet death, so that each simultaneous, mortally wounding bullet is necessary to the particular death (i.e., a two-bullet death) suffered by the victim shot by two defendants. Similarly, in the preemptive overdetermination cases, they assert that the first fire to arrive was necessary to the burning of the house, but the second was not, because had the first fire not happened the second fire still would have been prevented from burning the house (Lewis, 1970).

There are deep and well-known problems with all of these responses by the counterfactual theorists (Moore, 1999). Rather than pursue these, we should briefly consider modifications of the counterfactual test designed to end run some of these problems. With regard to the problem posed by the overdetermination cases, the best known alternative is to propose the NESS test: an event c causes an event e if and only if c is a necessary element in a set of conditions sufficient for e (Mackie; Wright, 1985). It is the stress on sufficiency that is supposed to end run the overdetermination problems. In the concurrent cause cases, where the two fires join to burn the victim's house, each fire is said to be a necessary element of its own sufficient set, so each fire is a cause. In the pre-emptive case, where the fires do not join and one arrives first, the first fire is a necessary element of a sufficient set, and so is the cause; but the second fire is not because absent from its set is the existence of a house to be burned.

There are problem with this NESS alternative too (Moore, 1999). For example, it is not stated how one individuates sets of conditions. Why aren't the two fires part of the same set, in which event neither is necessary? Also, in the preemptive case, isn't the addition of the condition, "existence of the victim's house at the time the second fire would be sufficient to destroy it," already sliding in the causal conclusion that the first fire already caused the house not to exist? Again these problems are not conclusive, and debate about them will no doubt continue for the foreseeable future. Such problems cause grave doubt to exist about any version of the counter-factual test among many legal theoreticians. Such academic doubts seem to have shaken the doctrinal dominance of the test very little, however.

Problems with the policy tests for legal cause. The main problem with both the ad hoc and the rule-based policy tests is that they seek to maximize the wrong policies. The general "functionalist" approach of such tests to legal concepts is correct: we should always ask after the purpose of the rule or institution in which the concept figures in order to ascertain its legal meaning. Yet the dominant purpose of the law's concept of causation is to grade punishment proportionately to moral blameworthiness. One who intentionally or recklessly causes a harm that another only tries to cause or risks causing, is more blameworthy (Moore, 1997, pp. 191–247). We must thus not seek the meaning of causation in extrinsic policies; rather, the legal concept of causation will serve its grading function only if the concept names some factual state of affairs that determines moral blameworthiness. By ignoring this dominant function of causation in criminal law, the explicit policy tests constructed an artificial concept of legal cause unusable in any just punishment scheme.

This problem does not infect the foreseeability and harm-within-the-risk tests. For those tests do seek to describe a factual state of affairs that plausibly determines moral blameworthiness. They are thus serving the dominant policy that must be served by the concept of causation in the criminal law. Their novelty lies in their reallocation of the locus of blame. On these theories, "legal cause" is not a refinement of an admitted desert-determiner, true causation; it is rather a refinement of another admitted desert-determiner, namely, mens rea (or "culpability").

Precisely because it is a culpability test, however, the foreseeability test becomes subject to another policy-based objection, that of redundancy. Why should we ask two culpability questions in determining blameworthiness? After we have satisfied ourselves that a defendant is culpable—either because she intended or foresaw some harm, or because she was unreasonable in not foreseeing some harm, given the degree of that harm's seriousness, the magnitude of its risk, and the lack of justification for taking such a risk—the foreseeability test bids us to ask, "was the harm foreseeable?" This is redundant, because any harm intended or foreseen is foreseeable, and any harm foreseeable enough to render an actor unreasonable for not foreseeing it, is also foreseeable.

The only way the foreseeability test avoids redundancy is by moving toward the harm-within-the-risk test. That is, one might say that the defendant was culpable in intending, foreseeing, or risking some harm type H, but that what his act in fact caused was an instance of harm type J; the foreseeability test of legal cause becomes nonredundant the moment one restricts it to asking whether J was foreseeable, a different question than the one asked and answered as a matter of mens rea about H. Yet this is to do the work of the harm-within-the-risk test, namely, the work of solving the "fit problem" of mens rea. Moreover, it is to do such work badly. Foreseeability is not the right question to ask in order to fit the harm in fact caused by a defendant to the type of harm he either intended to achieve or foresaw that he would cause. If the foreseeability test is to be restricted to this nonredundant work it is better abandoned for the harm-withinthe-risk test.

The main problem for the harm-within-the-risk test itself does not lie in any of the directions we have just explored. The test is in the service of the right policy in its seeking of a true desert-determiner, and the test does not ask a redundant question. To grade culpability by the mental states of intention, foresight, and risk we have to solve the fit problem above described. The real question for the harm-within-the-risk test is whether this grading by culpable mental states is all that is or should be going on under the rubric of "legal cause."

Consider in this regard two well-known sorts of legal cause cases. It is a time honored maxim of criminal law (as well as tort law) that "you take your victim as you find him." Standard translation: no matter how abnormal may be the victim's susceptibilities to injury, and no matter how unforeseeable such injuries may therefore be, a defendant is held to legally cause such injuries. Hit the proverbial thin-skulled man or cut the proverbial hemophiliac, and you have legally caused their deaths. This is hard to square with the harm-within-the-risk test. A defendant who intends to hit or to cut does not necessarily (or even usually) intend to kill. A defendant who foresees that his acts will cause the victim to be struck or cut, does not necessarily (or even usually) foresee that the victim will die. A defendant who negligently risks that his acts will cause a victim to be struck or cut is not necessarily (or even usually) negligent because he also risked death.

The second sort of case involves what are often called "intervening" or "superseding" causes. Suppose the defendant sets explosives next to a prison wall intending to blow up the wall and to get certain inmates out. He foresees to a practical certainty that the explosion will kill the guard on the other side of the wall. He lights the fuse to the bomb and leaves. As it happens, the fuse goes out. However: a stranger passes by the wall, sees the bomb, and relights the fuse for the pleasure of seeing an explosion; or, a thief comes by, sees the bomb and tries to steal it, dropping it in the process and thereby exploding it; or, lightning hits the fuse, reigniting it, and setting off the bomb; and so on. In all variations, the guard on the other side of the wall is killed by the blast. Standard doctrines of intervening causation hold that the defendant did not legally cause the death of the guard (Hart and Honore, 1985, pp. 133–185, 325–362). Yet this is hard to square with the harm-within-the-risk test. After all, did not the defendant foresee just the type of harm an instance of which did occur? Because the harm-within-the-risk question asks a simple type-to-token question—was the particular harm that happened an instance of the type of harm whose foresight by the defendant made him culpable—the test is blind to freakishness of causal route.

The American Law Institute's Model Penal Code modifies its adoption of the harm-withinthe-risk test in section 2.03 by denying liability for a harm within the risk that is "too remote or accidental in its occurrence to have a [just] bearing on the actor's liability or on the gravity of his offense." Such a caveat is an explicit recognition of the inability of the harm-within-the-risk test to accommodate the issues commonly adjudicated as intervening cause issues.

Such a recognition is not nearly broad enough to cover the inadequacy of the harm-within-the-risk approach. The basic problem with the test is that it ignores all of the issues traditionally adjudicated under the concept of legal cause. Not only is the test blind to freakishiness of causal route in the intervening cause situations, and to the distinction between antecedent versus after-arising abnormalities so crucial to resolution of the thin-skulled-man kind of issue, but the test also ignores all those issues of remoteness meant to be captured by Sir Francis Bacon's coinage, "proximate causation." Even where there is no sudden "break" in the chain of causation as in the intervening cause cases, there is a strong sense that causation peters out over space and time (Moore, 1999). Caesar's crossing the Rubicon may well be a necessary condition for my writing this article, but so many other events have also contributed that Caesar's causal responsibility has long since petered out. The logical relationship at the heart of the harm-within-the-risk test—"was the particular harm that happened an instance of the type of harm whose risk, foresight, or intention made the defendant culpable?"—is incapable of capturing this sensitivity to remoteness. As such, the harm-within-the-risk test is blind to the basic issue adjudicated under "legal cause." The harm-withinthe-risk test asks a good question, but it asks it in the wrong place.