What is the test for establishing "but for" causation in solicitor’s negligence cases?

The defendant then submits that even if the issue of negligence is a triable issue, causation of damages which also must be proved is not. Quoting from Folland, paras. 60 and 61: … On this analysis, the court looks for a causal connection between the wrongdoing of the defendant and the harm actually suffered by the plaintiff for which compensation is claimed. The link is established if the plaintiff demonstrates on the balance of probabilities that the harm would not have occurred but for the fault of the defendant, even if there are other factual causes that also meet the “but for” standard: Athey v. Leonati, supra. Absent the causal link, the defendant is not liable even though he may have been negligent. “But for” factual causation has been employed in solicitor’s negligence cases, particularly those where the plaintiff contends that he received negligent advice… In those cases, the plaintiff must show on the balance of probabilities that if properly advised, he would have proceeded in a manner that avoided the damages suffered or obtained the benefit lost as a result of the negligent advice…