You’ll find, below the cut, a brief digression on the meaning of “caused or contributed”, focusing on the meaning of “or” and applying both standard logic and legal logic.
What do I mean by legal logic?
I adopt the well-known, not always quoted completely, statement by Lord Halsbury in Quinn v. Leathem,  A. C. 495 (H.L.) at p. 506: “I entirely deny that it can be quoted for a proposition that may seem to follow logically from it. Such a mode of reasoning assumes that the law is necessarily a logical code, whereas every lawyer must acknowledge that the law is not always logical at all.” The complete passage from Quinn v Leathem is:
Now, before discussing the case of Allen v. Flood and what was decided therein, there are two observations of a general character which I wish to make, and one is to repeat what I have very often said before, that every judgment must be read as applicable to the particular facts proved, or assumed to be proved, since the generality of the expressions which may be found there are not intended to be expositions of the whole law, but governed and qualified by the particular facts of the case in which such expressions are to be found. The other is that a case is only an authority for what it actually decides. I entirely deny that it can be quoted for a proposition that may seem to follow logically from it. Such a mode of reasoning assumes that the law is necessarily a logical code, whereas every lawyer must acknowledge that the law is not always logical at all.
The last two sentences have been quoted in full, seemingly with approval, by provincial appellate courts and the Supreme Court of Canada. That occurred as early as Spencer v. Alaska Packers Association, 35 SCR 362 at 368, 1904 CanLII 23 and as recently as 1954 in The Queen v. Snider,  SCR 479 at 496-97 , 1954 CanLII 40. On occasion, the second sentence
from the quotation is omitted, as occurred in Doré v. Attorney General of Canada,  1 SCR 756 at 768, 1974 CanLII 153, or as in R. v. Henry,  3 SCR 609, 2005 SCC 76 where both are omitted when referring to the passage in Quinn v. Leathem as an explanation for an aspect of legal logic:
 every judgment must be read as applicable to the particular facts proved, or assumed to be proved, since the generality of the expressions which may be found there are not intended to be expositions of the whole law, but governed and qualified by the particular facts of the case in which such expressions are to be found.
I won’t call on common sense, because, as yet another judge of the United Kingdom Supreme Court has recently said “reliance on common sense (see Lord Hoffmann Common Sense and Causing Loss 1996), sometimes suggests that the author knows the result he seeks to achieve but is unable to articulate his reasons.” (See Menelaou v Bank of Cyprus UK Ltd  EWCA Civ 1960 at .)
In Jardine v. General Hydrogen Corporation, 2007 BCSC 119 (CanLII), the trial judge wrote:
 As one might expect, a body of jurisprudence has developed with respect to the interpretation of the word “or”. The potential interchangeability of the words “or” and “and” was recognized by the Supreme Court of Canada approximately a century ago in the decision in Clergue v. Vivian & Co. (1909),1909 CanLII 5 (SCC), 41 S.C.R. 607 at p. 617:
There is no doubt of the intention of the parties; and, where sense requires it, there are many cases to shew that we may construe the word “or” into “and”, and “and” into “or”, in order to effectuate the intent of the parties.
But since we already know (don’t we?) that for our purposes, in the context of the test for factual causation in tort, a cause must be a necessary cause, then what would “caused or contributed” mean if “or” means “and” so that “caused or contributed” is to be read as if it the phrase was “caused and contributed”. In the context of factual causation, “caused and contributed” would have to be understood to mean “caused, i.e., necessary for” plus “contributed, i.e., whatever contributed means.
But since we already know that since, at least according to the Supreme Court of Canada for claims subject to Canadian negligence law, ALL that is required for proof of factual causation is the necessity relationship between the negligent conduct and the injury, then “contributed” must refer to some other requirement that has to be satisfied for the factual cause to be treated as a legal cause.
If those of you who represent plaintiffs nonetheless want judges to instruct themselves, and juries, that under the but-for test, to establish the factual causation component of causation, your clients have to establish, on the balance of probability, both the necessity relationship and something else (whatever else that something might be: you don’t know what it is, and can’t provide a definition, but the judge or jury “will know it when it’s seen”) then go ahead. The defence side won’t mind in the slightest. Your clients might, though.
But if “contributed” isn’t, somehow, a label for something else that’s part of the factual causation component then what does it mean? What else could there be? What’s left other than the remoteness /proximate cause aspect of the causation requirement? No judge, to my knowledge, has ever asserted that in print; neither has any academic lawyer. I suggest that all of us who are familiar (enough) with the historical use of “caused or contributed” ought to agree that “contributed” was never used as a proxy for any portion of the remoteness / proximate cause concept.
I suppose we could look at the definitions of “or” in a relevant dictionary.
At least so long as the “Lower Mainland” portion of British Columbia remains physically attached to the portion of the North American continent containing Canada, the Canadian Oxford Dictionary (1998) will be an appropriate source for the definition of “or” relevant to the subject of this post. You’ll find that definition on p. 1021. Of the various choices, the relevant usage, serendipitously but no doubt coincidentally, is the first: “introducing the second of two alternatives (white or black)”. The explanation of the structure of the text at the beginning of the dictionary informs the reader that what one sees in the brackets (“white or black“) is an example of the usage of the word being defined.
Of course, that definition requires that we understand the meaning intended of “alternative” because, otherwise, we won’t know whether the meaning of “or” encompasses the possibility that “white” means “black”, as in the instance where we see (or hear) the the phrase “or, in other words” between two words or phrases.
Those of you who have a copy of Canadian Oxford Dictionary (1998) will
the find the definition of “alternative” on p. 37. I won’t quote it. The key concepts in the text of the relevant definitions are “mutually exclusive” or at least “different even if not mutually exclusive” as in (my examples here) “one or the other” or “this one or that one but not both”. Those of you who don’t have the book could check a good enough, for present purposes, on-line equivalent.
I assume those of you who, for whatever reason, are still here will agree that the ordinary meaning (usage) of “or”, to mean “alternative”, does not suggest that the meaning of the concept (word, phrase) on the left of the “X or Y” statement has the same meaning as the concept on the right. That is, X does not equal Y.
In passing, when I saw that the definition of “alternative” was only on p. 37 of the book, I was a bit disappointed but then I realized that p. 37 is close enough to p. 42, physically and otherwise for present purposes. The physical component does not require explanation. One explanation of “otherwise” would seem to captured by what follows. (Keep in mind the Quinn v Leathem admonition and the refrain often heard in the legal profession that the lawyer went to law school because he or she could not handle math. No, I’m not one of that group. I went to law school because I was accepted and the school’s hockey team needed a goalie.)
1. 3 + 7 = 10
2. 4 + 2 = 6
3. 6 is 60% of 10
divided by 42 is 88.095% of 42.
5. Both 60% and 88.095% are more than 50% plus 1, so the relationship between 42 and 37 satisfies the balance of probabilities.
6. [There is no step 6. One of the Bruces took it.]
7. Recall statement (1): 3 +7 = 10. Note that 4 +4 + 2 also equals 10.
8. If we subtract 4 from each side of the second equation in (7), the result is 4 + 2 = 6. (Subtracting one “4” is a good idea, too, because “4” is an unlucky number in a major culture on Earth.)
9. Thus, for present purposes, the position represented by the statement in proposition (1) is equivalent to the position represented by the statement in proposition (2) from which it follows that the position of the definition of “alternative” on p. 37 of the dictionary may be treated, for present purposes, as if it appeared on p. 42. (This is known as a “legal fiction” which, apparently, is more seemingly acceptable than fantasy or science fiction but not necessarily on par with Canadian fiction.)
10. In the alternative, the Earth is flat. (See Quinn v. Leathem, above.)