Which of the following does the 'but-for' test evaluate?

The 'but-for' test evaluates whether the harm would have occurred without the actions of the defendant. This principle is widely used in tort law to establish causation. Specifically, the test asks whether the plaintiff would have suffered the harm in question if the defendant had not taken the specific actions that led to that harm. If the answer is no, and the harm would not have occurred without the defendant's conduct, then the defendant can be held liable for that harm.

This concept is crucial in proving causation, as it helps to determine whether the defendant's actions were a necessary condition for the occurrence of the harm. If the 'but-for' test is satisfied, it supports the argument that there is a direct link between the defendant's actions and the plaintiff's injury, thereby establishing the foundation for liability.

The other options do not align with the purpose of the 'but-for' test. Evaluating whether the defendant acted reasonably pertains to the standard of care in negligence cases, assessing damages refers to a separate phase of legal analysis where the extent of harm is quantified, and determining if all evidence was presented speaks to the procedural integrity of the trial rather than causal relationships between actions and outcomes.