Aggregation and law.

• Author: Porat, Ariel
• Position: Introduction through II. Contract Law, p. 2-34

INTRODUCTION I. TORT LAW A. Factual Aggregation B. Normative Aggregation and Mixed Aggregation C. Cross-Person Aggregation II. CONTRACT LAW A. Factual Aggregation B. Normative Aggregation C. Cross-Person Aggregation III. CRIMINAL LAW A. Factual Aggregation B. Normative Aggregation C. Cross-Person Aggregation IV. PUBLIC LAW A. Factual Aggregation B. Normative Aggregation C. Cross-Person Aggregation V. EXPLANATIONS AND PROPOSALS A. The Arbitrariness of Legal Boundaries B. Other Explanations for Failures To Aggregate and Possible Objections to Aggregation 1. Corrective Justice 2. Incommensurability 3. Cognitive Limitations C. Implementation 1. Sword and Shield 2. One Trial 3. Crafting Remedies CONCLUSION INTRODUCTION

Suppose you are invited to dinner by a friend. You are a bit tired, but not extremely tired, so that reason by itself would not make you decline the invitation. You also want to spend the evening with your family, but this reason standing alone would not convince you to stay at home. Finally, you are also a bit pressed for time because you need to prepare a lecture for tomorrow, but once again you would not miss the dinner for that reason only. It is quite plausible that even if none of these reasons, standing alone, is sufficient for you to decline the invitation, the aggregation of all three reasons would be sufficient. Nevertheless, we suspect that most people, while aggregating the three reasons for themselves and declining the invitation, would not say to their friend that they cannot come to dinner because: (1) they are tired; (2) they want to spend the evening with their family; and (3) they need to prepare a lecture for tomorrow and are therefore pressed for time. They would instead choose the strongest of the three reasons and provide it as the sole reason for declining the invitation.

Consider another possibility. Your friend invites you to dinner a week in advance. Peering into the future, you predict that with some (low) probability you will be too tired, that with some (low) probability your children will need help with their homework, and that with some (low) probability you will need to prepare for work on the following day. You realize that while each event will individually come to pass with low probability, the probability that at least one of the events will come to pass is quite high. Even so, you would not say to your friend (if you want to keep your friendship) that while each reason you have for turning down the invitation is low probability, they are jointly high probability. Most likely, you would turn down the invitation on the basis of the most probable reason.

These puzzles, which we call "aggregation puzzles," have counterparts in the law. Consider a plaintiff who brings two separate claims against the defendant arising from the same event, a car accident. The plaintiff argues that the defendant committed a strict liability tort by driving an inherently dangerous vehicle and, in the alternative, that the defendant caused a tort through negligent driving. To win on the strict liability claim, the plaintiff must prove that the vehicle was inherently dangerous, but the plaintiff can provide evidence to show only a 40% probability of inherent dangerousness. In addition, the plaintiff can show only a 40% probability of negligence. A court would hold against the plaintiff on both claims because she cannot meet the 50% preponderance-of-the-evidence threshold for either claim. However, if the two claims are independent, (1) the plaintiff can show a 64% probability that the defendant committed either one tort or the other. (2) Yet courts do not permit this type of cross-claim factual aggregation.

For another example, this one involving claims arising from two distinct events, consider a plaintiff who can prove with 40% probability that the defendant engaged in a material breach of a contract, and also can prove with 40% probability that the defendant engaged in fraudulent misrepresentation to induce the creation of the contract. Under either theory, the plaintiff would be entitled to rescission of the contract. Yet again, although the probability that at least one claim is valid is 64% (assuming that the claims are independent), the plaintiff would lose, because courts do not permit cross-claim factual aggregation.

A second type of factual aggregation, which we will call cross-element factual aggregation, occurs across the elements that make up a single claim. For example, a negligence claim has elements of fault and causation, each of which the plaintiff must prove to establish liability. Say the plaintiff can prove each with 60% probability. If the probabilities of the two elements are not aggregated, the plaintiff wins, because the probability of each element being valid is higher than 50%, and so the plaintiff has established all requisite elements of her claim. But if the probabilities of the elements are aggregated, the plaintiff loses, because the probability that the defendant was at fault and caused the harm is only 36%. (3) There is uncertainty about whether and to what extent courts engage in cross-element factual aggregation.

A third type of factual aggregation, which we call within-element factual aggregation, occurs when the plaintiff proposes several alternative factual theories that satisfy a single element of a claim. Say, for example, that the plaintiff suing for negligence has two distinct theories for why the defendant was at fault, and she can prove that each theory is true with 40% probability. If the probabilities of the two theories are not aggregated, the plaintiff will fail to establish the element of fault by preponderance of the evidence. If the probabilities are aggregated, however, the plaintiff will successfully establish fault, because the probability that one theory or the other is true is 64%. Unlike cross-claim factual aggregation, within-element factual aggregation is routine in American jurisprudence.

Aggregation does not always require uncertainty. Suppose that a plaintiff can show with certainty that the defendant induced the creation of a contract with misleading remarks that fall just short of fraudulent misrepresentation, and that the defendant subsequently engaged in a breach that falls just short of material. A court would typically not grant rescission, but not because the plaintiff failed to establish facts with sufficient probability. The plaintiff would lose because, for each claim, she failed to allege sufficient wrongdoing. Yet one could argue that--even if each is insufficient standing alone--the two bad acts together justify rescission.

We will call this type of aggregation normative aggregation. Like factual aggregation, it has cross-claim, cross-element, and within-element variations. Combining the independently insufficient claims for fraudulent misrepresentation and material breach described above, for example, would entail cross-claim normative aggregation. The normative weights of the two claims, neither of which standing alone is sufficient to establish liability, would be aggregated, and the combined weight of the two claims would establish liability.

Although courts do not usually permit this type of aggregation, such aggregation does occur in one important class of cases. When a neutral and generally applicable statute burdens religious exercise alone, it does not violate the First Amendment. But if the law simultaneously burdens another constitutional right, such as the right to free speech--even if that burden is not sufficient to violate that constitutional right independently--the law may nonetheless be overturned because of the aggregate burden it imposes on two constitutional rights. (4)

One can also imagine cases that share aspects of cross-claim factual aggregation and cross-claim normative aggregation. Suppose that the plaintiff can prove material breach with 40% probability, and can prove with certainty that the defendant induced the creation of the contract with misleading remarks that fall just short of fraudulent misrepresentation. One might argue that the plaintiff should be entitled to rescind the contract, but courts do not permit this type of cross-claim mixed aggregation.

Another type of aggregation takes place across persons. Suppose that a firm pollutes the air, and ten nearby residents claim that they were injured by the pollution. Each resident can show that she breathed in the pollution and that her medical condition deteriorated after the pollution, but all residents suffer from preexisting respiratory ailments, and thus cannot show with probability above 50% that the pollution, rather than their preexisting conditions, caused their harm. They would therefore lose their cases. Yet if each resident could show that the probability that the pollution exacerbated her medical condition is, say, 10%, then the residents can collectively prove that the probability that at least one of them was injured was greater than 50%, and therefore that the firm should pay damages (5) (although not necessarily everyone's damages-an issue we will address later). We will call this type of aggregation cross-person aggregation. Cross-person aggregation could be factual, as in the preceding example, but could also be normative or mixed. (6)

These examples illustrate an important vulnerability at the heart of the law. They reflect the fact that law relies on legal categories that organize the judicial treatment of disputes. These categories operate at different levels of generality, including bodies of law (tort, contract), claims (strict liability, negligence), and elements (offer, acceptance, breach, harm). These categories are important, and it is hard to imagine how the law would work without them. But they also require courts to disregard information that is relevant to an overall evaluation of the asserted wrongdoing.

This happens in the ways we have illustrated. First, where two claims concern a...