for the proposition that "proof of negligence in the air, so to speak, will not do." Only if there is a duty to the injured plaintiff, the breach of which causes injury, can there be liability. He defended his decision, "a different conclusion will involve us, and swiftly too, in a maze of contradictions." Cardozo posed hypothetical situations: if a railway guard stumbles over a bundle of newspapers, and there are explosives within, will there be liability to an injured passenger at the other end of the platform? Will the result be different if the object containing the explosives is a valise instead? If there was negligence that day, Cardozo argued, it was only negligence that resulted in the fall and destruction of the package, and there was no wrong done by the railroad to Palsgraf for personal injury, "the diversity of incidents emphasizes the futility of the effort to build the plaintiff's right upon the basis of a wrong to some one else." The chief judge instructed, "The risk reasonably to be perceived defines the duty to be obeyed". Cardozo did not absolve the defendant who knowingly unleashes a destructive force, such as by shooting a gun, just because the bullet takes an unexpected path. This is not such a case, Cardozo held: even if the railway guard had thrown down the package intentionally, without knowing the contents he could not knowingly risk harm to Palsgraf, and would not be liable. Negligence cannot impose liability where an intentional act would not. Negligence, Cardozo emphasized, derives from human relations, not in the abstract. Negligence that does no one harm is not a tort. It is not enough, he found, to prove negligence by the defendant and damage to the plaintiff; there must be a breach of duty owed to the plaintiff by the defendant. He traced the history of the law of negligence, a concept not known in medieval times, and noted that it evolved as an offshoot of the law of trespass, and one could not sue for trespass to another. Had the railroad been negligent towards Palsgraf, it might have been liable, but "the consequences to be followed must first be rooted in a wrong", and there was no legal wrong done by the railroad to Palsgraf. Thus, the lower courts were incorrect, and must be reversed, and the case dismissed, with Palsgraf to bear the costs of