Because a defendant is not liable , no matter how reckless his conduct , unless he owes a duty to the plaintiff . according to the accepted definition of restatement second of tort , negligence is conduct , which falls below the standard established by law for the protection of others against unreasonable risk of harm 美國第二次侵權(quán)法重述給過失侵權(quán)下的定義是:過失侵權(quán)是指一個(gè)人沒有在法律所規(guī)定的,以保護(hù)其他人免受不合理的傷害危險(xiǎn)的法律義務(wù)范圍內(nèi)行為。