[11] The fourth and final question to address in a negligence claim is whether the defendant’s breach caused the plaintiff’s harm in fact and in law. The evidence before the trial judge establishes that the defendant’s breach of its duty of care in fact caused Mr. Mustapha’s psychiatric injury. We are not asked to revisit this conclusion. The remaining question is whether that breach also caused the plaintiff’s damages in law or whether they are too remote to warrant recovery.

[12] The remoteness inquiry asks whether “the harm [is] too unrelated to the wrongful conduct to hold the defendant fairly liable” (Linden and Feldthusen, at p. 360). Since The Wagon Mound (No. 1), the principle has been that “it is the foresight of the reasonable man which alone can determine responsibility” (Overseas Tankship (U.K.) Ltd. v. Morts Dock & Engineering Co., [1961] A.C. 388 (P.C.), at p. 424).

[13] Much has been written on how probable or likely a harm needs to be in order to be considered reasonably foreseeable. The parties raise the question of whether a reasonably foreseeable harm is one whose occurrence is probable or merely possible. In my view, these terms are misleading. Any harm which has actually occurred is “possible”; it is therefore clear that possibility alone does not provide a meaningful standard for the application of reasonable foreseeability. The degree of probability that would satisfy the reasonable foreseeability requirement was described in The Wagon Mound (No. 2) as a “real risk”, i.e. “one which would occur to the mind of a reasonable man in the position of the defendant … and which he would not brush aside as far-fetched” (Overseas Tankship (U.K.) Ltd. v. Miller Steamship Co. Pty., [1967] A.C. 617, at p. 643).

[14] The remoteness inquiry depends not only upon the degree of probability required to meet the reasonable foreseeability requirement, but also upon whether or not the plaintiff is considered objectively or subjectively. One of the questions that arose in this case was whether, in judging whether the personal injury was foreseeable, one looks at a person of “ordinary fortitude” or at a particular plaintiff with his or her particular vulnerabilities. This question may be acute in claims for mental injury, since there is a wide variation in how particular people respond to particular stressors. The law has consistently held — albeit within the duty of care analysis — that the question is what a person of ordinary fortitude would suffer: see White v. Chief Constable of South Yorkshire Police, [1998] 3 W.L.R. 1509 (H.L.); Devji v. Burnaby (District) (1999), 180 D.L.R. (4th) 205, 1999 BCCA 599; Vanek. As stated in White, at p. 1512: “The law expects reasonable fortitude and robustness of its citizens and will not impose liability for the exceptional frailty of certain individuals.”

[15] As the Court of Appeal found, at para. 49, the requirement that a mental injury would occur in a person of ordinary fortitude, set out in Vanek, at paras. 59-61, is inherent in the notion of foreseeability. This is true whether one considers foreseeability at the remoteness or at the duty of care stage. As stated in Tame v. New South Wales (2002), 211 C.L.R. 317, [2002] HCA 35, per Gleeson C.J., this “is a way of expressing the idea that there are some people with such a degree of susceptibility to psychiatric injury that it is ordinarily unreasonable to require strangers to have in contemplation the possibility of harm to them, or to expect strangers to take care to avoid such harm” (para. 16). To put it another way, unusual or extreme reactions to events caused by negligence are imaginable but not reasonably foreseeable.

[16] To say this is not to marginalize or penalize those particularly vulnerable to mental injury. It is merely to confirm that the law of tort imposes an obligation to compensate for any harm done on the basis of reasonable foresight, not as insurance. The law of negligence seeks to impose a result that is fair to both plaintiffs and defendants, and that is socially useful. In this quest, it draws the line for compensability of damages, not at perfection, but at reasonable foreseeability. Once a plaintiff establishes the foreseeability that a mental injury would occur in a person of ordinary fortitude, by contrast, the defendant must take the plaintiff as it finds him for purposes of damages. As stated in White, at p. 1512, focusing on the person of ordinary fortitude for the purposes of determining foreseeability “is not to be confused with the ‘eggshell skull’ situation, where as a result of a breach of duty the damage inflicted proves to be more serious than expected”. Rather, it is a threshold test for establishing compensability of damages at law.

[17] I add this. In those cases where it is proved that the defendant had actual knowledge of the plaintiff’s particular sensibilities, the ordinary fortitude requirement need not be applied strictly. If the evidence demonstrates that the defendant knew that the plaintiff was of less than ordinary fortitude, the plaintiff’s injury may have been reasonably foreseeable to the defendant. In this case, however, there was no evidence to support a finding that Culligan knew of Mr. Mustapha’s particular sensibilities.