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Reasonable Foreseeability:
Principles Regarding Whether an Advance Risk of Harm Arising Could Be Recognized
Last Updated: June 11 2026
Question: What does “reasonable foreseeability” mean in Ontario negligence law, and how can it affect my claim?
Answer: In Ontario negligence cases, “reasonable foreseeability” is an objective test asking whether a reasonable person in the defendant’s position should have anticipated a real risk of the kind of harm that occurred, assessed without 20/20 hindsight, and it helps courts decide fault and whether the harm is too remote to be compensable, as discussed in Rankin (Rankin’s Garage & Sales) v. J.J., [2018] 1 S.C.R. 587 and Mustapha v. Culligan of Canada Ltd., [2008] 2 S.C.R. 114. Vescio Legal Services is a Paralegal serving clients across Ontario, offering clear, practical guidance on whether foreseeability supports your case and the steps to pursue fair compensation; call (416) 400-8255 to get started.
Understanding Foreseeability Principles
In negligence law, the principle of reasonable foreseeability applies. Simply put, reasonable foreseeability means the common sense thinking ahead and understanding of what might happen as a result of certain conduct. As the core definition of negligence involves the failure to do, or avoid doing, what a reasonably acting person who do, or would avoid doing, an understanding of what a reasonably acting person might perceive as posing a risk is required.
The Law
The concept of reasonable foreseeability was explained by the Supreme Court within the cases of Rankin (Rankin’s Garage & Sales) v. J.J., [2018] 1 S.C.R. 587, and Mustapha v. Culligan of Canada Ltd., [2008] 2 S.C.R. 114, as follows:
[53] Whether or not something is “reasonably foreseeable” is an objective test. The analysis is focussed on whether someone in the defendant’s position ought reasonably to have foreseen the harm rather than whether the specific defendant did. Courts should be vigilant in ensuring that the analysis is not clouded by the fact that the event in question actually did occur. The question is properly focussed on whether foreseeability was present prior to the incident occurring and not with the aid of 20/20 hindsight: L. N. Klar and C.S.G. Jefferies, Tort Law (6th ed. 2017), at p. 212.
[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 defendan[t] . . . and which he would not brush aside as far-fetched” (Overseas Tankship (U.K.) Ltd. v. Miller Steamship Co. Pty., [1967] A.C. 617 (P.C.), 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.”
The Rankin and Mustapha cases describe the foreseeability question as relating to whether an individual could sensibly foresee that certain behavior might culminate in the occurrence of harm to another person. Furthermore, following the guidance of Rankin and Mustapha cases, while evaluating whether harm was foreseeable, a court should approach the question from a retro-active yet forward-looking perspective instead of looking back perspective after an incident has actually occurred..
Conclusion
Negligence law encompasses the assessment of whether an individual behaved with an unreasonable lack of care and should be deemed responsible for harm brought about by such lack of care. Within the inquiry of whether the behavior lacked due care is the question regarding whether the ensuing harm could be reasonably anticipated. If the harm was reasonably unforeseeable, then liability for the harm fails to arise.
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