concerned. International jurisprudence on causation In Snell v Farrell [1990] 2 SCR 311 at 320, 326-7, Sopinka J, delivering the judgment of the Supreme Court of Canada, said: The traditional approach to causation has come under attack in a number of cases in which there is concern that due to the complexities of proof, the probable victim of tortious conduct will be deprived of relief. This concern is strongest in circumstances in which, on the basis of some percentage of statistical probability, the plaintiff is the likely victim of the combined tortious conduct of a number of defendants, but cannot prove causation against a specific defendant or defendants on the basis of particularized evidence in accordance with traditional principles. The challenge to the traditional approach has manifested itself in cases dealing with nontraumatic injuries such as man-made diseases resulting from the widespread diffusion of chemical products, including product liability cases in which a product which can cause injury is widely manufactured and marketed by a large number of corporations ... Reversing the burden of proof may be justified where two defendants negligently fire in the direction of the plaintiff and then by their tortious conduct destroy the means of proof at his disposal. In such a case it is clear that the injury was not caused by neutral conduct. It is quite a different matter to compensate a plaintiff by reversing the burden of proof for an injury that may very well be due to factors unconnected to the defendant and not the fault of anyone. In March v E & MH Stramare Pty Ltd (1991) 171 CLR 506 at 508, Mason CJ, sitting in the High Court of Australia, did not "accept that the 'but for' (causa sine qua non) test ever was or now should become the exclusive test of causation in negligence cases" and added (at p 516): The 'but for' test gives rise to a well-known difficulty in cases where there are two or more acts or events which would each be sufficient to bring about the plaintiff's injury. The application of the test 'gives the result, contrary to common sense, that neither is a cause': Winfield and Jolowicz on Tort, 13th ed (1989), p. 134. In truth, the application of the test proves to be either inadequate or troublesome in various situations in which there are multiple acts or events leading to the plaintiff's injury: see, e.g., Chapman v Hearse, Baker v Willoughby [1970] AC 467; McGhee v National Coal Board; M'Kew (to which I shall shortly refer in some detail). The cases demonstrate the lesson of experience, namely, that the test, applied as an exclusive criterion of causation, yields unacceptable results and that the results which it yields must be tempered by the making of 36