“Causation” — Sometimes called the “but-for” test, causation is the relationship between an act and the consequences it produces.
An action for negligence requires proof of a duty of care, breach of the standard of care, compensable damage, and — causation.
The legal test for causation requires the plaintiff to show on a balance of probabilities that “but for” the defendant’s negligent act, the injury would not have occurred.
Clements v. Clements, 2012 SCC 32,  2 S.C.R. 181
“A trial judge is to take a robust and pragmatic approach to determining if a plaintiff has established that the defendant’s negligence caused her loss. Scientific proof of causation is not required.”
Athey v. Leonati  3 SCR 458, 1996 CanLII 183
Causation is established where the defendant’s negligence “materially contributed” to the occurrence of the injury.