As the Writ System that prevailed in England until the nineteenth century defined particular rules and procedures for each Form of Action, so today our modern causes of action take to themselves a host of idiosyncratic details. Until recently the common law had long conceived of tort and contract law not as parts of a general law of obligation but as separate bodies of rules divided by a boundary wall that kept each from invading the territory of the other. New developments in the law have breached this wall in places and allowed tort to intrude into domains traditionally ruled by contract. But this process is far from complete, and many differences still remain between actions in contract and tort.