Recovery in negligence presupposes a relationship between the plaintiff and defendant based on the existence of a duty of care — a defendant who is at fault and a plaintiff who has been injured by that fault. If the defendant breaches this duty and thereby causes injury to the plaintiff, the law “corrects” the deficiency in the relationship by requiring the defendant to compensate the plaintiff for the injury suffered. This basis for recovery, sometimes referred to as “corrective justice”, assigns liability when the plaintiff and defendant are linked in a correlative relationship of doer and sufferer of the same harm: E. J. Weinrib, The Idea of Private Law (1995), at p. 156.
Clements v. Clements, 2012 SCC 32 at para. 7.
This isn’t short.
Reductio ad absurdum is
A method of proof which proceeds by stating a proposition and then showing that it results in a contradiction, thus demonstrating the proposition to be false.
See Wolfram MathWorld: http://mathworld.wolfram.com/ReductioadAbsurdum.html
The validity of this method of refuting a proposition was acknowledged by the Supreme Court of Canada as early as 1914 and as recently as 2000. See Townsend v. Northern Crown Bank, 49 SCR 394 at 397-98 (“That is almost a reductio ad absurdum, and Mr. Laidlaw, of course, did not assume any such untenable position, rather he tried to escape for it.”) and R. v. Proulx, 2000 SCC 5 at para. 53,  1 SCR 61 (used to describe an analysis leading to a “penalogical paradox”).
In Canada v. Craig, 2012 SCC 43 at paras. 24-31, the Court referred briefly to the principles that govern when it will overrule one its prior decisions, stating that “overturning a precedent of this Court is a step not to be lightly undertaken. This is especially so when the precedent represents the considered views of firm majorities” (para. 24) – referring to the Court’s decision in Ontario (Attorney General) v. Fraser, 2011 SCC 20,  2 S.C.R. 3 at paras. 56-57. The Court also wrote in Craig that “the Court must be satisfied based on compelling reasons that the precedent was wrongly decided and should be overruled.” (para. 25).
The text of paras. 56-57 of Ontario (Attorney General) v. Fraser is:
 Our colleague correctly recognizes at the outset of his reasons that overturning a precedent of this Court is a step not to be lightly undertaken. We would note that as we understand the law (see above), rejection of Health Services implies rejection of Dunmore as well, since the two cases rest on the same fundamental logic.
 The seriousness of overturning two recent precedents of this Court, representing the considered views of firm majorities, cannot be overstated. This is particularly so given their recent vintage. Health Services was issued only four years ago, and, when this appeal was argued, only two years had passed.
(per McLachin CJ and Lebel J., Binnie, Fish and Cromwell JJ concurring.)
The full statement of the principles that govern the Court’s competence to overrule its own decisions, or otherwise change existing common law, appears in Bank of America Canada v. Mutual Trust Co,  2 S.C.R. 601 at para. 43, 2002 SCC 43, the Supreme Court summarized its rules setting out setting out when it is appropriate for the Court to depart from that jurisprudence :
(1) to keep the common law in step with the evolution of society,
(2) to clarify a legal principle, or
(3) to resolve an inconsistency.
… [T]he changes should be incremental, and their consequences capable of assessment.
See also Transport North American Express Inc. v. New Solutions Financial Corp.,  1 S.C.R. 249 at para. 65, 2004 SCC 7 and and Friedmann Equity Developments Inc. v. Final Note Ltd.,  1 S.C.R. 842 at para. 43, 2000 SCC 34.
The rationale the Supreme Court provided in Craig for this diffidence is:
 Courts must proceed with caution when deciding to overrule a prior decision. In Queensland v. Commonwealth (1977), 139 C.L.R. 585 (H.C.A.), at p. 599, Justice Gibbs articulated the required approach succinctly:
No Justice is entitled to ignore the decisions and reasoning of his predecessors, and to arrive at his own judgment as though the pages of the law reports were blank, or as though the authority of a decision did not survive beyond the rising of the Court. A justice, unlike a legislator, cannot introduce a programme of reform which sets at nought decisions formerly made and principles formerly established. It is only after the most careful and respectful consideration of the earlier decision, and after giving due weight to all the circumstances, that a Justice may give effect to his own opinions in preference to an earlier decision of the Court.
The Supreme Court had earlier explained this diffidence in Watkins v. Olafson,  S.C.R. 750 at 760, 1989 CanLII 36 (per McLachlin J, as she then was):
The court may not be in the best position to assess the deficiencies of the existing law, much less problems which may be associated with the changes it might make. The court has before it a single case; major changes in the law should be predicated on a wider view of how the rule will operate in the broad generality of cases. Moreover, the court may not be in a position to appreciate fully the economic and policy issues underlying the choice it is asked to make.
In Clements v. Clements, 2012 SCC 32, the Court wrote at para. 16
 Elimination of proof of causation as an element of negligence is a “radical step that goes against the fundamental principle stated by Diplock L.J. in Browning v. War Office,  3 All E.R. 1089 (C.A.), at pp. 1094-95: ‘…[a] defendant in an action in negligence is not a wrongdoer at large; he is a wrongdoer only in respect of the damage which he actually causes to the plaintiff’”: Mooney v. British Columbia, 2004 BCCA 402 (CanLII), 2004 BCCA 402, 202 B.C.A.C. 74, at para. 157, per Smith J.A., concurring in the result. For that reason, recourse to a material contribution to risk approach is necessarily rare, and justified only where it is required by fairness and conforms to the principles that ground recovery in tort.
If, as para. 16 of Clements seems to state, we are to understand the material contribution doctrine as explained in Clements and Resurfice Corp. Ltd. v. Hanke,  1 S.C.R. 333, 2007 SCC 7, as a doctrine which eliminates proof of causation as an element of the cause of action in negligence, then where, in either Clements or Resurfice, or any other Supreme Court of Canada decision, do we find the Court explaining why eliminating the requirement of proof of causation was appropriate in light of the principles it had set out in Bank of America Canada v. Mutual Trust Co?
(1) [T]o keep the common law in step with the evolution of society, (2) to clarify a legal principle, or (3) to resolve an inconsistency. … [T]he changes should be incremental, and their consequences capable of assessment.
We see, in both Clements and Resurfice, statements that this step is required as a matter of fairness and justice. Clements, for example, states at para. 16 that the step is “justified only where it is required by fairness and conforms to the principles that ground recovery in tort.”
It seems to me that the first of the three principles is central. Can we say that the change was necessary to keep the common law “in step with the evolution of Canadian society”? While the U.K. House of Lords thought it was necessary for U.K. society, the Australian High Court has so far declined to incorporate, into Australian common law, the material contribution to risk doctrine as an alternative method for proving causation in negligence. See, most recently, Amaca Pty Ltd v Booth;  HCA 53. Is Canadian society closer to U.K. society than Australian?
Perhaps we can take the Court’s restriction of the material contribution to risk principle to cases involving two or more tortfeasors where the negligence of each would be a but-for cause if the negligence of all of the others had not occurred as the Court’s attempt to keep the change incremental and the consequences capable of assessment.
But what if the Clements explanation of when material contribution applies
46(2) Exceptionally, a plaintiff may succeed by showing that the defendant’s conduct materially contributed to risk of the plaintiff’s injury, where (a) the plaintiff has established that her loss would not have occurred “but for” the negligence of two or more tortfeasors, each possibly in fact responsible for the loss; and (b) the plaintiff, through no fault of her own, is unable to show that any one of the possible tortfeasors in fact was the necessary or “but for” cause of her injury, because each can point to one another as the possible “but for” cause of the injury, defeating a finding of causation on a balance of probabilities against anyone.
is, on its face, applicable to every action where the plaintiff has been involved in successive incidents, where it is not the case that negligence in the successive incidents were cumulatively necessary causes of at least some of the injury and damages? (Or using a well known example, the case is not Athey.)
We’ll put aside, for this discussion, the question of what is fair, or just, or conforms to the principles that govern recovery in tort, in holding a person liable for damage that, by legal definition, that person did not cause. That is necessarily the consequence of the Clements explanation of the basis of the material contribution doctrine. At least one of the negligent persons’ conduct was, for law,
not a cause not a probable factual cause, at least based on a valid application of the but-for test which we are told, again, is the only approved method of establishing factual causation. (As a past fact, that conclusion is taken to be a certainty even though only established as a probability: Athey)* Is it now a tenet of Canadian society that people who, in law, did not cause any of the compensable damages may be held liable for all of it?
[*amendment made Aug 7, 2012]
Well … actually, it is. It’s called vicarious liability. So let’s look at something from our seminal case on that concept: Bazley v. Curry,  2 SCR 534, 1999 CanLII 692
 However, effective compensation must also be fair, in the sense that it must seem just to place liability for the wrong on the employer. Vicarious liability is arguably fair in this sense. The employer puts in the community an enterprise which carries with it certain risks. When those risks materialize and cause injury to a member of the public despite the employer’s reasonable efforts, it is fair that the person or organization that creates the enterprise and hence the risk should bear the loss. This accords with the notion that it is right and just that the person who creates a risk bear the loss when the risk ripens into harm. While the fairness of this proposition is capable of standing alone, it is buttressed by the fact that the employer is often in the best position to spread the losses through mechanisms like insurance and higher prices, thus minimizing the dislocative effect of the tort within society. “Vicarious liability has the broader function of transferring to the enterprise itself the risks created by the activity performed by its agents” (London Drugs, per La Forest J., at p. 339).
But (there’s always a but) isn’t it the case that, for at least one of multiple wrongdoers win the situations to which the Clements material contribution doctrine applies, law presumes the risk that that person created did not ripen into harm? (In negligence law, past events are treated as as certainties once held probable.)
Of course, in the vicarious liability situation the justification is the principal’s / employer’s relationship with the actual wrongdoer and the idea that the former created the opportunity for the wrongdoer to commit the wrong. But that rationale doesn’t apply in the material contribution situation.
So if the justification isn’t that the creation of the opportunity for the wrong, or that the risk created by any one particular wrongdoer actually ripened into harm, then what is the justification for the material contribution doctrine according to the Supreme Court?
The Court could have said, in Clements – after all they did mention Cook v. Lewis,  SCR 830 at 832-33, 834-35, 1951 CanLII 26 – that the negligence of each of the wrongdoers’ “essentially destroyed the victim’s power of proof”. Rand J. wrote, in Cook:
What, then, the culpable actor has done by his initial negligent act is, first, to have set in motion a dangerous force which embraces the injured person within the scope of its probable mischief; and next, in conjunction with circumstances which he must be held to contemplate, to have made more difficult if not impossible the means of proving the possible damaging results of his own act or the similar results of the act of another. He has violated not only the victim’s substantive right to security, but he has also culpably impaired the latter’s remedial right of establishing liability. By confusing his act with environmental conditions, he has, in effect, destroyed the victim’s power of proof.
The legal consequence of that is, I should say, that the onus is then shifted to the wrongdoer to exculpate himself; it becomes in fact a question of proof between him and the other and innocent member of the alternatives, the burden of which he must bear. The onus attaches to culpability, and if both acts bear that taint, the onus or prima facie transmission of responsibility attaches to both, and the question of the sole responsibility of one is a matter between them.
… This is a case where each hunter would know of or expect the shooting by the other and the negligent actor has culpably participated in the proof-destroying fact, the multiple shooting and its consequences. No liability will, in any event attach to an innocent act of shooting, but the culpable actor, as against innocence, must bear the burden of exculpation.
But Rand J’s judgment wasn’t the majority explanation and the explanation is a rationale for shifting the onus only. That, apparently, wasn’t where the Clements panel wanted to go.
And, but, it’s really stretching a point to suggest that, where a plaintiff has been involved in successive motor vehicle accidents (for example), the allegedly negligent drivers in any of the incidents “would know of or expect” the negligence of any of the others.
So, the key words are the highlighted words in the last sentence: “but the culpable actor, as against innocence, must bear the burden”. That, not surprisingly, is essentially the rationale of the majority in Cook, at 842, where the majority adopted the rationale from some U.S. decisions, albeit not put quite so bluntly as “make the negligent person pay”.
… We think that … each is liable for the resulting injury to the boy, although no one can say definitely who actually shot him. To hold otherwise would be to exonerate both from liability, although each was negligent, and the injury resulted from such negligence.”
When we consider the relative position of the parties and the results that would flow if plaintiff was required to pin the injury on one of the defendants only, a requirement that the burden of proof on that subject be shifted to defendants becomes manifest. They are both wrongdoers-both negligent toward plaintiff. They brought about a situation where the negligence of one of them injured the plaintiff, hence, it should rest with them each to absolve himself if he can. The injured party has been placed by defendants in the unfair position of pointing to which defendant caused the harm. If one can escape the other may also and plaintiff is remediless. Ordinarily defendants are in a far better position to offer evidence to determine which one caused the injury.
[Emphasis in original.]
Clements summary of the Cook rationale appears in para. 19: “To deny him recovery, while allowing the negligent defendants to escape liability by pointing the finger at each other, would not have met the goals of negligence law of compensation, fairness and deterrence, in a manner consistent with corrective justice.”
But, don’t forget that Cook allows the defendant an out. The defendant will not be held liable if the defendant can rebut the onus. But, if a defendant can rebut the onus, in a situation to which Cook applies, then that situation turns out to not be could never have been one to which the Clements explanation for qualifying impossibility applies. We should assume the Clements panel saw this.
And, in the successive incident situation, it’s stretching a point to claim that the negligence of a later wrongdoer destroyed the plaintiff’s ability to prove causation in respect of an earlier wrongdoing, unless one means that because the the injuries are “indivisible” it’s impossible for the court to make a valid conclusion as to who caused what. But, if the injuries are indivisible, we don’t need Clements material contribution to establish factual causation, do we?
You might say “hold on now, indivisible injury presumes a finding that each of tortious acts could have been, in fact, a but-for cause of the injury.”
I’ll say, right. But if each of the tortious acts could have been a but-for cause, isn’t that the Clements explanation of the circumstances to which material contribution apply? What, then, is the status of the indivisible injury doctrine for instances where all of the alleged causes are tortious?
In any event, is the rationale of the Clements explanation for material contribution “make the negligent person pay because the person has been negligent and there is a possibility that that person’s negligence was the cause and as between the innocent person and the wrongdoer the wrongdoer ought to pay?” Even if, in fact, there was no causal connection? But because of the possibility of a causal connection?
Because liability is required by “corrective justice”? The Court wrote, at para. 32: “to allow the defendants to each escape liability by pointing the finger at one another would have been at odds with the fairness, deterrence, and corrective justice objectives of the law of negligence.”; and, at para. 41:
 In these circumstances, permitting the plaintiff to succeed on a material contribution to risk basis meets the underlying goals of the law of negligence. Compensation for injury is achieved. Fairness is satisfied; the plaintiff has suffered a loss due to negligence, so it is fair that she turns to tort law for compensation. Further, each defendant failed to act with the care necessary to avoid potentially causing the plaintiff’s loss, and each may well have in fact caused the plaintiff’s loss. Deterrence is also furthered; potential tortfeasors will know that they cannot escape liability by pointing the finger at others. And these goals are furthered in a manner consistent with corrective justice; the deficit in the relationship between the plaintiff and the defendants viewed as a group that would exist if the plaintiff were denied recovery is corrected. The plaintiff has shown that she is in a correlative relationship of doer and sufferer of the same harm with the group of defendants as a whole, if not necessarily with each individual defendant.
The Court also wrote at para. 37, that corrective justice is the “anchor” of the law of negligence. (I mention in passing that “anchor” can be used in a sense that is antithetical to the laudatory meaning used by the Court.)
Is that corrective justice as it is generally understood by the by the majority of corrective justice scholars? No – especially not, in my view, corrective justice as explained by the source quoted by the Court. Consider this recent explanation by Professor Weinrib:
Corrective justice is the theoretical notion that sets out what it means for private law to be fair and coherent. It does so by insisting that liability be based on normative considerations that embrace both parties in relation to each other. The requirement of applicability to both parties in their interrelationship is a general structural idea to which particular substantive elements of liability, whatever they are, have to conform if they are to be fair to both parties and coherent with one another.
Consider the treatment of unreasonable risk creation in negligence. Negligence law translates into a series of legal concepts the progression from the defendant’s creation of an unreasonable risk to the materialization of that risk in injury to the plaintiff. The termini of this progression are the concepts of breach of the standard of reasonable care and factual causation. These two termini, however, do not operate as atomistic elements, one applying to the defendant and the other to the plaintiff, that the law simply adds together. Rather, the law insists that the termini be coherently linked through the concepts of duty and proximate cause. These concepts, in turn, connect wrongdoing and injury by describing the wrongful risk in terms of the range of the potential victims and consequences through which the risk is to be understood as wrongful. Thus, the risk that materializes into injury to the plaintiff is the same as the risk that the defendant unreasonably created, and the wrong done in its creation is the same as the wrong suffered in its materialization. Through this ensemble of concepts, all of which are necessary for liability, the law treats the defendant’s act and its effect on the plaintiff as an integrated sequence in which there is a single injustice that is the same for both parties.
Ernest J Weinrib, “The Structure of Unjustness” (2012) 92 Boston University Law Review 1067 at 1067-68, 1069-70 (internal footnote omitted, emphasis added).
But we know that, with respect to at least one of the wrongdoers in the scenario to which the Clements explanation of material contribution applies, the risk that that person created did not materialize into injury.
‘The question is,’ said Alice, ‘whether you can make words mean so many different things.’
‘The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.’
Lewis Carroll, Through the Looking Glass, c.6.
Or, putting this in legal terms, bearing in mind that lawyers stand even lower in the pecking order than judicial officers and (at least if you accept the views of some judges, lawyers writing academically even lower yet), so make the appropriate substitutions.
 Any legal system which has a judicial appeals process inherently creates a pecking order for the judiciary regarding where judicial decisions stand on the legal ladder.
 I am bound by decisions of Queen’s Bench judges, by decisions of the Alberta Court of Appeal and by decisions of the Supreme Court of Canada. Very simply, Masters in Chambers of a superior trial court occupy the bottom rung of the superior courts judicial ladder.
 I do not overrule decisions of a judge of this court. The judicial pecking order does not permit little peckers to overrule big peckers. It is the other way around.
South Side Woodwork v. R.C. Contracting (1989), 95 A.R. 161, 1989 CanLII 3384 (AB QB, Master).