CALABRESI, Circuit Judge:

Luis Liriano was severely injured on the job in 1993 when his hand was caught in a meat grinder manufactured by Hobart Corporation (“Hobart”) and owned by his employer, Super Associated (“Super”). The meat grinder had been sold to Super with a safety guard, but the safety guard was removed while the machine was in Super's possession and was not affixed to the meat grinder at the time of the accident. The machine bore no warning indicating that the grinder should be operated only with a safety guard attached.

Liriano sued Hobart under several theories, including failure to warn. Hobart brought a third-party claim against Super. The United States District Court for the Southern District of New York (Shira A. Scheindlin, J.) dismissed all of Liriano's claims except the one based on failure to warn, and the jury returned a verdict for Liriano on that claim. It attributed five percent of the liability to Hobart and ninety-five percent to Super. The district court then held a partial retrial limited to the issue of whether and to what extent Liriano was responsible for his own injury. On that retrial, the jury assigned Liriano one-third of the fault.

Before she entered judgment based on these calculations, Judge Scheindlin granted Liriano's motion to add $21,252.34 to the total damage award. The increase reflected the amount of a hospital bill that had been submitted to the jury during trial but somehow had not been included in the initial damage calculation.

Hobart and Super appealed, arguing (1) that as a matter of law, there was no duty to warn, and (2) that even if there had been a duty to warn, the evidence presented was not sufficient to allow the failure-to-warn claim to reach the jury. Super further argued (3) that the district court erred in holding a retrial on the issue of Liriano's comparative fault without also retrying Hobart's and Super's shares of fault relative to each other, *267 and (4) that the district court's addition of the hospital bill to its damage calculation was an impermissible additur. We certified questions (1) and (2) to the New York Court of Appeals. See Liriano I, 132 F.3d at 132. That Court answered question (1) in Liriano's favor, saying that there can indeed be a duty to warn in a case like this one. See Liriano II, 92 N.Y.2d at 243, 700 N.E.2d at 309, 677 N.Y.S.2d at 770. The Court of Appeals, however, declined to answer question (2). See id.

DISCUSSION

A. Sufficiency of the Evidence

Hobart makes two arguments challenging the sufficiency of the evidence. The first concerns the obviousness of the danger that Liriano faced, and the second impugns the causal relationship between Hobart's negligence and Liriano's injury. Each of these arguments implicates issues long debated in the law of torts. With respect to the asserted clarity of the danger, the question is when a danger is so obvious that a court can determine, as a matter of law, that no additional warning is required. With respect to causation, the issue is whether a jury may infer that a defendant's particular negligence was the cause-in-fact of a plaintiff's actual injury from the general fact that negligence like the defendant's tends to cause injuries like the plaintiff's. The obviousness question was the subject of an important but now generally rejected opinion by Justice Holmes, then on the Massachusetts Supreme Judicial Court; FN1 the causation question is answered in a celebrated opinion of Judge Cardozo, then on the New York Court of Appeals.FN2 We examine each in turn. #p#分页标题#e#

(1) Obviousness

[1] More than a hundred years ago, a Boston woman named Maria Wirth profited from an argument about obviousness as a matter of law that is very similar to the one Hobart urges today. See Lorenzo v. Wirth, 170 Mass. 596, 49 N.E. 1010 (1898). Wirth was the owner of a house on whose property there was a coal hole. See id. at 599, 49 N.E. at 1010. The hole abutted the street in front of the house, and casual observers would have no way of knowing that the area around the hole was not part of the public thoroughfare. See id. at 599, 49 N.E. at 1011. A pedestrian called Lorenzo fell into the coal hole and sued for her injuries. See id. Writing for a majority of the Supreme Judicial Court of Massachusetts, Oliver Wendell Holmes, Jr., held for the defendant. He noted that, at the time of the accident, there had been a heap of coal on the street next to the coal hole, and he argued that such a pile provided sufficient warning to passers-by that they were in the presence of an open hole. “A heap of coal on a sidewalk in Boston is an indication, according to common experience, that there very possibly may be a coal hole to receive it.” Id. at 601, 49 N.E. at 1011. And that was that.

It was true, Holmes acknowledged, that “blind men, and foreigners unused to our ways, have a right to walk in the streets,” id. at 600, 49 N.E. at 1011, and that such people might not benefit from the warning that piles of coal provided to sighted Bostonians. But Holmes wrote that coal-hole cases were simple, common, and likely to be oft repeated, and he believed it would be better to establish a clear rule than to invite fact-specific inquiries in every such case. “In simple cases of this sort,” he explained, “courts have felt able to determine what, in every case, however complex, defendants are bound at their peril to know.” Id. With the facts so limited, this was an uncomplicated case in which the defendant could, as a matter of law, rely on the plaintiff's responsibility to know what danger she faced.

Justice Knowlton disagreed. See id. at 601-04, 49 N.E. at 1011-13 (Knowlton, J., dissenting). His opinion delved farther into the particular circumstances than did Holmes's opinion for the majority. In so doing, he showed that Lorenzo's failure to appreciate her peril might have been foreseen by Wirth and hence that Wirth's failure *268 to warn might constitute negligence. He noted, for example, that the accident occurred after nightfall, when Lorenzo perhaps could not see, or recognize, the heap of coal for what it was. See id. at 603, 49 N.E. at 1012. There was “a throng of persons” on the street, such that it would have been difficult even in daylight to see very far ahead of where one was walking. See id. at 603-04, 49 N.E. at 1012. And the plaintiff was, in fact, a foreigner unused to Boston's ways. “[S]he had just come from Spain, and had never seen coal put into a cellar through a coal hole.” Id. at 603, 49 N.E. at 1012. In sum, the case was not the “simple” one that Holmes had made it out to be. What is more, none of the facts he recited was either unusual or unforeseeable by Wirth. “What kind of conduct is required under complex conditions, to reach the usual standard of due care, namely, the ordinary care of persons of common prudence, is a question of fact .... [and thus] a question for a jury.” Id. at 604, 49 N.E. at 1012-13 (emphasis added). Even cases involving “obvious” dangers like coal holes, Knowlton believed, might not be resolvable as matters of law when viewed in the fullness of circumstances that rendered the issue less clear than it would be when posed in the abstract. #p#分页标题#e#

Holmes commanded the majority of the Supreme Judicial Court in 1898, but Knowlton's position has prevailed in the court of legal history. “ ‘[T]he so-called Holmes view-that standards of conduct ought increasingly to be fixed by the court for the sake of certainty-has been largely rejected.... The tendency has been away from fixed standards and towards enlarging the sphere of the jury.’ ” Fowler V. Harper, Fleming James, Jr., & Oscar S. Gray, The Law of Torts § 15.3, at 358-59 n. 16 (2d ed.1986) (hereinafter Harper & James) (quoting Nuckoles v. F.W. Woolworth Co., 372 F.2d 286, 289 (4th Cir.1967)).

The courts of New York have several times endorsed Knowlton's approach and ruled that judges should be very wary of taking the issue of liability away from juries, even in situations where the relevant dangers might seem obvious, and especially when the cases in question turn on particularized facts. See, e.g., Havas v. Victory Paper Stock Co., 49 N.Y.2d 381, 388, 402 N.E.2d 1136, 1139-40, 426 N.Y.S.2d 233, 237 (1980) (stating that negligence is an issue “particularly appropriate to leave ... to the jury” because of the “idiosyncratic nature of most tort cases” and because “reasonableness” is generally appropriate for jury resolution); Cabri v. Long Island R.R. Co., 306 N.Y. 765, 118 N.E.2d 475 (1954) (holding that the danger of crossing railroad tracks is not so obvious as to prevent the issue of contributory negligence from reaching the jury).FN3 See also Stagl v. Delta Airlines, Inc., 52 F.3d 463, 470-71 (2d Cir.1995) (noting the demise of the Holmes position and collecting cases); Fleming James, Jr., Geoffrey C. Hazard, Jr., & John Leubsdorf, Civil Procedure § 7.21, at 371 (4th ed.1992) (stating that the decline of the Holmes view has been especially pronounced in tort suits for personal injury); Harper & James, § 17.2, at 571-72 nn. 8-13, 573-74 nn. 22-26, 576-78 nn. 33-37 (collecting many authorities).

But the secular decline of the Holmes position and the concomitant tendency of the New York Court of Appeals to permit issues of obviousness to go to the jury do not fully dispose of the question before us. After all, as Holmes himself might have cautioned, general trends are far from conclusive in concrete cases. Cf. Lochner v. New York, 198 U.S. 45, 75, 25 S.Ct. 539, 49 L.Ed. 937 (1905) (Holmes, J., dissenting). And it is not surprising that there have been situations in which New York state courts have deemed dangers to be sufficiently clear so that warnings were, as a matter of law, not necessary. See, e.g., Dickerson v. George J. Meyer Mfg., 248 A.D.2d 970, 971, 669 N.Y.S.2d 1001, 1002 (4th Dep't 1998) (holding that there is no duty to warn of the danger of closely examining the mechanical workings of a machine while the machine is operating); Pigliavento v. Tyler Equip. Corp., 248 A.D.2d 840, 842, 669 N.Y.S.2d 747, 749 (3d Dep't 1998) (holding that there is no duty to warn of the *269 danger of falling from an unguarded platform on a concrete mixer truck); Caris v. Mele, 134 A.D.2d 475, 476, 521 N.Y.S.2d 260, 261 (2d Dep't 1987) (holding that there is no duty to warn of the danger of diving headfirst into an above-ground swimming pool only four feet deep). #p#分页标题#e#

If the question before us were, therefore, simply whether meat grinders are sufficiently known to be dangerous so that manufacturers would be justified in believing that further warnings were not needed, we might be in doubt. On one hand, just as a coal hole was deemed a danger appreciated by most Bostonians in 1898, so most New Yorkers would probably appreciate the danger of meat grinders a century later. Any additional warning might seem superfluous. On the other hand, Liriano was only seventeen years old at the time of his injury and had only recently immigrated to the United States. He had been on the job at Super for only one week. He had never been given instructions about how to use the meat grinder, and he had used the meat grinder only two or three times. And, as Judge Scheindlin noted, the mechanism that injured Liriano would not have been visible to someone who was operating the grinder. It could be argued that such a combination of facts was not so unlikely that a court should say, as a matter of law, that the defendant could not have foreseen them or, if aware of them, need not have guarded against them by issuing a warning. That argument would draw strength from the Court of Appeals' direction that the question of whether a warning was needed must be asked in terms of the information available to the injured party rather than the injured party's employer, see Liriano II, 92 N.Y.2d at 241, 700 N.E.2d at 308, 677 N.Y.S.2d at 769, and its added comment that “in cases where reasonable minds might disagree as to the extent of the plaintiff's knowledge of the hazard, the question is one for the jury.” Id.

Nevertheless, it remains the fact that meat grinders are widely known to be dangerous. Given that the position of the New York courts on the specific question before us is anything but obvious, we might well be of two minds as to whether a failure to warn that meat grinders are dangerous would be enough to raise a jury issue.FN4

The Court of Appeals' decision in Garcia v. Biro Mfg. Co., 63 N.Y.2d 751, 469 N.E.2d 834, 480 N.Y.S.2d 316 (1984), cuts the opposite way. It can be read to imply that the danger of operating meat grinders without safety guards is not obvious as a matter of law. But it, too, is not conclusive. Garcia denied summary judgment for the defendant-manufacturer, letting a strict liability claim for meat grinder injuries go forward, because the defendant had not adequately demonstrated that the meat grinder had a safety guard when it was manufactured. See id. It follows, one might argue, that under New York law a manufacturer could be held strictly liable for injuries caused by guardless meat grinders and hence that the lack of a safety guard is a design defect under New York law. Under the consumer expectation test, an obvious danger does not make a product defective, because no implied warranty is breached. See Castro v. QVC Network, Inc., 139 F.3d 114, 116-18 (2d Cir.1998) (discussing the various New York tests for product defects). One could therefore conclude that the danger posed by meat grinders lacking safety guards is not deemed obvious as a matter of law in New York. We are reluctant, however, to claim that this reasoning represents the thinking of the Court of Appeals. Garcia may imply this result, but it did not directly address any question beyond that of the requirements for summary judgment in the case before it. As a result, we think it imprudent to read so many inferences into Garcia's cursory statement. Like Hernandez, Garcia is merely suggestive; and faced with these contradictory suggestions, we cannot make any confident prediction as to what New York's highest court might hold. We believe it wisest, therefore, to say that the law on this point is not settled. #p#分页标题#e#

Hobart sees the matter differently. For the proposition that New York clearly considers the danger obvious, it cites Cramer v. Toledo Scale Co., 158 A.D.2d 966, 551 N.Y.S.2d 718 (4th Dep't 1990). In that case, the manufacturer of a meat grinder had been sued on several theories, including failure to warn, after an eight-year-old boy severely injured his hand in the grinder. See id. at 966, 551 N.Y.S.2d at 719. The Appellate Division upheld a grant of summary judgment in favor of the manufacturer on the failure-to-warn claim. See id. at 966, 551 N.Y.S.2d at 719. But Cramer did not hold that the danger was obvious; the Appellate Division decided the case on the issue of causation, not that of obviousness. It held that the facts of the case showed that the absence of a warning was not a cause of the accident and that the victim, being only eight years old, was not in a foreseeable category of plaintiffs. See id. at 966-67, 551 N.Y.S.2d at 719-20. It therefore did not discuss whether the plaintiff needed to be warned. Cf. Palsgraf v. Long Island R. Co., 248 N.Y. 339, 162 N.E. 99 (1928).

Cramer also addressed the question of whether the manufacturer should have warned the victim's parents. It stated that there is “no necessity to warn a customer already aware-through common knowledge or learning-of a specific hazard,” Cramer, 158 A.D.2d at 967, 551 N.Y.S.2d at 720 (emphasis added), and that it was “clear from the record that the [the victim's parents] were fully aware of the dangers,” id. (emphasis added). Contrary to Hobart's contention, then, Cramer does not hold that meat grinders are obviously dangerous as a matter of law. It holds, unremarkably, that the absence of a warning is not the legal cause of an accident when the uncontroverted record demonstrates that the plaintiff already knew everything the warning would have conveyed. Indeed, one could argue that by resolving the issue on the basis of what the record showed about the victim's parents' actual knowledge, rather than holding that they must have known as a matter of law, Cramer suggests that the relevant question is one of fact.
*270 But to state the issue that way would be to misunderstand the complex functions of warnings. As two distinguished torts scholars have pointed out, a warning can do more than exhort its audience to be careful. It can also affect what activities the people warned choose to engage in. See James A. Henderson, Jr., and Aaron D. Twerski, Doctrinal Collapse in Products Liability: The Empty Shell of Failure to Warn, 65 N.Y.U. L.Rev. 265, 285 (1990). And where the function of a warning is to assist the reader in making choices, the value of the warning can lie as much in making known the existence of alternatives as in communicating the fact that a particular choice is dangerous. It follows that the duty to warn is not necessarily obviated merely because a danger is clear.

To be more concrete, a warning can convey at least two types of messages. One states that a particular place, object, or activity is dangerous. Another explains that people need not risk the danger posed by such a place, object, or activity in order to achieve the purpose for which they might have taken that risk. Thus, a highway sign that says “Danger-Steep Grade” says less than a sign that says “Steep Grade Ahead-Follow Suggested Detour to Avoid Dangerous Areas.” #p#分页标题#e#

If the hills or mountains responsible for the steep grade are plainly visible, the first sign merely states what a reasonable person would know without having to be warned. The second sign tells drivers what they might not have otherwise known: that there is another road that is flatter and less hazardous. A driver who believes the road through the mountainous area to be the only way to reach her destination might well choose to drive on that road despite the steep grades, but a driver who knows herself to have an alternative might not, even though her understanding of the risks posed by the steep grade is exactly the same as those of the first driver. Accordingly, a certain level of obviousness as to the grade of a road might, in principle, eliminate the reason for posting a sign of the first variety. But no matter how patently steep the road, the second kind of sign might still have a beneficial effect. As a result, the duty to post a sign of the second variety may persist even when the danger of the road is obvious and a sign of the first type would not be warranted.

One who grinds meat, like one who drives on a steep road, can benefit not only from being told that his activity is dangerous but from being told of a safer way. As we have said, one can argue about whether the risk involved in grinding meat is sufficiently obvious that a responsible person would fail to warn of that risk, believing reasonably that it would convey no helpful information. But if it is also the case-as it is-that the risk posed by meat grinders can feasibly be reduced by attaching a safety guard, we have a different question. Given that attaching guards is feasible, does reasonable care require that meat workers be informed that they need not accept the risks of using unguarded*271 grinders? Even if most ordinary users may-as a matter of law-know of the risk of using a guardless meat grinder, it does not follow that a sufficient number of them will-as a matter of law-also know that protective guards are available, that using them is a realistic possibility, and that they may ask that such guards be used. It is precisely these last pieces of information that a reasonable manufacturer may have a duty to convey even if the danger of using a grinder were itself deemed obvious.

Consequently, the instant case does not require us to decide the difficult question of whether New York would consider the risk posed by meat grinders to be obvious as a matter of law. A jury could reasonably find that there exist people who are employed as meat grinders and who do not know (a) that it is feasible to reduce the risk with safety guards, (b) that such guards are made available with the grinders, and (c) that the grinders should be used only with the guards. Moreover, a jury can also reasonably find that there are enough such people, and that warning them is sufficiently inexpensive, that a reasonable manufacturer would inform them that safety guards exist and that the grinder is meant to be used only with such guards. Thus, even if New York would consider the danger of meat grinders to be obvious as a matter of law, that obviousness does not substitute for the warning that a jury could, and indeed did, find that Hobart had a duty to provide. It follows that we cannot say, as a matter of law, that Hobart had no duty to warn Liriano in the present case. We therefore decline to adopt appellants' argument that the issue of negligence was for the court only and that the jury was not entitled, on the evidence, to return a verdict for Liriano. #p#分页标题#e#

(2) Causation

On rebriefing following the Court of Appeals decision, Hobart has made another argument as to why the jury should not have been allowed to find for the plaintiff. In this argument, Hobart raises the issue of causation. It maintains that Liriano “failed to present any evidence that Hobart's failure to place a warning [on the machine] was causally related to his injury.” Whether or not there had been a warning, Hobart says, Liriano might well have operated the machine as he did and suffered the injuries that he suffered. Liriano introduced no evidence, Hobart notes, suggesting either that he would have refused to grind meat had the machine borne a warning or that a warning would have persuaded Super not to direct its employees to use the grinder without the safety attachment.

Hobart's argument about causation follows logically from the notion that its duty to warn in this case merely required Hobart to inform Liriano that a guard was available and that he should not use an unguarded grinder. The contention is tightly reasoned, but it rests on a false premise. It assumes that the burden was on Liriano to introduce additional evidence showing that the failure to warn was a but-for cause of his injury, even after he had shown that Hobart's wrong greatly increased the likelihood of the harm that occurred. But Liriano does not bear that burden. When a defendant's negligent act is deemed wrongful precisely because it has a strong propensity to cause the type of injury that ensued, that very causal tendency is evidence enough to establish a prima facie case of cause-in-fact. The burden then shifts to the defendant to come forward with evidence that its negligence was not such a but-for cause.