Respondeat superior (Latin: "let the master answer"; plural: respondeant superiores) is a doctrine that a party is responsible for (and has vicarious liability for) acts of their agents. For example, in the United States, there are circumstances when an employer is liable for acts of employees performed within the course of their employment. This rule is also called the master-servant rule, recognized in both common law and civil law jurisdictions. In a broader scope, respondeat superior is based upon the concept of vicarious liability. In common law The common law concept of respondeat superior has its roots in ancient Rome. At the time, the concept applied to slaves, as that was the meaning of what has been translated as servants, and it applied if the slave could not pay himself for the act. It was later expanded to apply to not only slaves but also animals and family members of the master of a family. In 1698, the doctrine was mentioned in dicta by Sir Holt in the English case of Jones v. Hart, 2 Salk 441, 90 Eng. Rep. (K.B. 1698). In the US, it was discussed in the case of Wright v. Wilcox, 19 Wend. 343, 32 Am. Dec. 508 (1838), in which a boy climbed on a wagon driven by defendant's servant, who drove his horses faster, which caused the boy to be thrown and injured. The judge ruled that the master was not responsible under respondeat superior because the servant had acted in a way in driving the horses that the master had not assented to and so it was not within the scope of his employment. US Supreme Court Justice Oliver Wendell Holmes Jr. opined in 1891, "It is hard to explain why a master is liable to the extent he is for the negligent acts of one who, at the time, really is his servant, acting within the general scope of his employment. Probably master and servant are 'feigned to be all one person' by a fiction". He was of the view that the doctrine was in opposition to common sense. In 1916, the British attorney Thomas Baty wrote that the doctrine, which he called a "deep-pocket theory", was "derived from an inconsiderate use of precedents and a blind reliance on the slightest word of an eminent judge, and from the mistaken notion that his flights of imagination ... were actual decided cases". When