1
An Alternative to the Basic Causal Requirement
for Liability under the Negligence Rule
Steven Shavell
*
The primary causal requirement that must be met for a negligent party to be held liable for a
harm is a demonstration that the harm would not have occurred if the party had not been
negligent. Thus, for a speeding driver to be found liable for harm done in a car accident, it must
be shown that the accident would not have happened if the driver had obeyed the speed limit.
The main point made here is that this basic causal requirement may be difficult to satisfy and
hence may interfere with the discouragement of negligence. Therefore, an alternative and
usually easier-to-meet causal requirement is proposed—that the harm would not have occurred
if the party not been engaged in his activity (if the driver had not been driving).
1. Introduction
In this article I will suggest that the principal causal requirement for a finding of liability under
the negligence rule may needlessly hamper deterrence of negligent conduct; and in light of that, I
will consider a possibly advantageous alternative requirement.
At present, a negligent party cannot be held liable for a harm unless the party’s negligence was a
cause in fact of the harm—meaning that the harm would not have occurred if the party’s conduct
had not been negligent, that is, if the party had instead exercised reasonable care.
1
Suppose that a
driver negligently speeds on a city street and strikes a pedestrian on a crosswalk, whereas if the
driver had been traveling at the speed limit, he would have been able to stop short of the
*
Samuel R. Rosenthal Professor of Law and Economics, Harvard Law School, and Research Associate, National
Bureau of Economic Research. I thank John Goldberg, Marcel Kahan, Louis Kaplow, A. Mitchell Polinsky, and
David Rosenberg for advice and comments on this article, Daniel Belgrad, Tuhin Chakraborty, Heather Pincus, and
Lisa Wang for able research assistance, and the John M. Olin Center for Law, Economics, and Business at Harvard
University for research support.
1
See Restatement, Third, Torts: Liability for Physical and Emotional Harm (hereafter “Restatement Third”) § 26
Factual Cause, stating that “Tortious conduct must be a factual cause of harm for liability to be imposed. Conduct is
a factual cause of harm when the harm would not have occurred absent the conduct.” See also Becht and Miller
(1961) and Dobbs, Hayden, and Bublick (2016) ch.14. For the most part, I will use the terms cause in fact, factual
cause, or sometimes simply cause in this article instead of other commonly employed synonyms, notably, actual
cause, but for cause, necessary cause, and cause sine qua non. Additionally, I note that Restatement Third, § 27
Multiple Sufficient Causes, accords wider meaning to the term factual cause. To avoid distracting issues, however, I
will restrict attention to the definition of factual cause of § 26. Finally, I observe that in other Common Law
countries and in civil law countries generally, negligence must also be shown to be a cause in fact of harm for a
party to be held liable for it; see, for example, Infantino and Zervogianni (2017). Thus the § 26 cause-in-fact
requirement for liability under the negligence rule appears to be a universal feature of tort law.
