When someone makes a mistake, the law refers to this as “negligence”. For example, a driver who makes a left turn in the face of oncoming traffic, resulting in a crash, will likely be found to have been negligent. The law then holds the negligent person responsible for the damages he or she has caused. But how does the law determine what damages have been caused by the negligence?
Generally, the injured person will be compensated for any damages which would not have occurred “but for” the negligent conduct. If the injured person had pre-existing back pain which was worsened by the crash, the law will require the negligent person to compensate the injured person for the difference in their pain and ability to function, but not for the pre-existing problems. If the injured person fractured his leg in the crash, and his leg was previously fine, he would be compensated for the full extent of the leg injury and related problems.
In essence, causation is simply the relationship that must be found to exist between the negligence of the defendant and the injury to justify compensation. Without causation, there can be no compensation.