A more thorough explanation:

Definition: Merged Causes is a legal term used when two or more defendants breach their duties towards a plaintiff, but it is difficult to prove which defendant's breach caused the plaintiff's harm. In such cases, the court uses the "substantial factor test" to determine if each defendant's breach was a substantial factor in causing the harm, even if it did not cause the harm on its own. If a defendant's breach is deemed a substantial factor, they can be held liable for the harm caused to the plaintiff.

Example: Suppose a person is injured in a car accident caused by two drivers who were both speeding and ran a red light. In this case, both drivers breached their duty to drive safely and caused harm to the plaintiff. However, it is difficult to determine which driver's breach caused the plaintiff's injuries. Using the substantial factor test, the court would examine whether each driver's breach was a substantial factor in causing the harm. If both drivers' breaches were deemed substantial factors, they could be held jointly and severally liable for the plaintiff's injuries.

Explanation: The example illustrates how merged causes can occur in a car accident case where two drivers breach their duty to drive safely and cause harm to a plaintiff. The court uses the substantial factor test to determine if each driver's breach was a substantial factor in causing the harm, even if it did not cause the harm on its own. If both drivers' breaches are deemed substantial factors, they can be held jointly and severally liable for the plaintiff's injuries.