What is the test for establishing that negligence was the sole cause of injury?

244 In Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458 (S.C.C), at p. 467, Major, J. stated: It is not now necessary, nor has it ever been, for the plaintiff to establish that the defendant’s negligence was the sole cause of the injury. There will frequently be a myriad of other background events which were necessary preconditions to the injury occurring. To borrow an example from Professor Fleming (The Law of Torts) (8th ed. 1992) at p. 193, a “fire ignited in a wastepaper basket is… caused not only by the dropping of a lighted match, but also by the presence of combustible material and oxygen, a failure of the cleaner to empty the basket and so forth”. As long as a defendant is part of the cause of an injury, the defendant is liable, even though his act alone was not enough to create the injury. There is no basis for a reduction of liability because of the existence of other preconditions: defendants remain liable for all injuries caused or contributed to by their negligence.