“For want of a nail, the kingdom was lost,” as the old saying has it. Virtually any cause of an injury can be traced to some preceding cause. The problem for the law is to know when to draw the line between causes that are immediate and causes too remote for liability reasonably to be assigned to them. In tort theory, there are two kinds of causes that a plaintiff must prove: actual cause and proximate cause. Actual cause (causation in fact) can be found if the connection between the defendant’s act and the plaintiff’s injuries passes the “but for” test: if an injury would not have occurred “but for” the defendant’s conduct, then the defendant is the cause of the injury. Still, this is not enough causation to create liability. The injuries to the plaintiff must also be foreseeable, or not “too remote,” for the defendant’s act to create liability. This is proximate cause: a cause that is not too remote or unforseeable.
Suppose that the person who was injured was not one whom a reasonable person could have expected to be harmed. Such a situation was presented in one of the most famous US tort cases, Palsgraf v. Long Island Railroad (Cases ), which was decided by Judge Benjamin Cardozo. Although Judge Cardozo persuaded four of his seven brethren to side with his position, the closeness of the case demonstrates the difficulty that unforeseeable consequences and unforeseeable plaintiffs present.