Why is a principal usually not liable for the negligent physical conduct of a nonservant agent?

In Anglo-American law, the liability of a principal for the torts of an agent is primarily governed by the doctrine of respondeat superior, which is rooted in the master-servant relationship.1

A principal is generally not liable for the negligent physical conduct of a nonservant agent because the doctrine of respondeat superior—and the resulting vicarious liability—presupposes a degree of physical control by the master over the servant. This level of control, such as that exercised over a delivery truck driver, is typically absent in relationships with nonservant agents, such as factors or brokers.1

While a principal may be held liable for other torts committed by a nonservant agent—specifically those that are authorized or made possible by the agent's position, such as tortious misrepresentation—the lack of physical control over the agent's actions precludes the application of vicarious liability for general negligent physical conduct.1