AT THE END OF PALSGRAF, THERE IS CHAOS - AN ASSESSMENT OF PROXIMATE CAUSE IN LIGHT OF CHAOS THEORY

Palsgraf articulated the doctrine of proximate cause, necessary to pro ve the tort of negligence. Palsgraf needs to be reexamined in light of today's understanding of cause and effect. The case concerned a woman (Mrs. Palsgraf) standing on a train platform who was injured by a roo f tile that fell as the result of the vibrations caused by the explosi on of another passenger's package. Mrs. Palsgraf sued the railway for negligence and prevailed at the trial court level. The New York Court of Appeals reversed the trial court, however, holding that the railway company's actions were not the proximate cause of Mrs. Palsgraf's inj uries. Modern science recognizes that the railway station constituted a complex dynamic system. Palsgraf was decided in 1928 at a time when understanding of cause and effect in complex dynamics was minimal and steeped in a linear mind-set. Because the understanding of cause and e ffect in these systems has been significantly advanced by the field of nonlinear dynamics in recent years, the case should be reexamined in this new light. Linear systems have outputs that are proportional to t heir inputs and are therefore predictable. But linearity inadequately models most of the real world. Nonlinear systems, though not recognize d by most as such, are more prevalent than linear systems and have out puts disproportionate to their input. A subset within the group of non linear systems are chaotic systems, the main focus of this essay. The title ''chaotic'' is misleading as these systems still follow discrete physical laws. Bur it is their sensitivity to initial conditions that makes them unpredictable. What appears as a random result may actuall y be a strong reaction to immeasurable inputs at the beginning of a se quence of events. The weather is a good example of this principle, ter med deterministic chaos. There is no way to isolate and define each in itial condition that goes into a weather pattern, but as will be shown , each initial condition may radically affect the resulting systems. C haotic systems exist alongside predictable linear systems. In Palsgraf , the train station had both regular, predictable systems, such as the track being able to carry the weight of the train, and some unpredict able, chaotic systems, such as the interaction of the exploding packag e, the roof tiles, and Mrs. Palsgraf. If an accident happened that inv olved a regular system, then it is more likely that the railway should have been held liable. This is because the engineers who designed the station should have known the linear parameters within which the stat ion could be used safely. Had they neglected to act on this knowledge, the company would have been negligent. However, because the system in volved was a high dimension chaotic system-many interacting degrees of freedom-the system was subject to the principle of sensitivity to ini tial conditions, and Mrs. Palsgraf's injuries were in no way foreseeab le or direct even though chaos theory elucidates the causal link betwe en explosion and injury. Because they were in no way foreseeable or di rect, the defendant had no duty toward the plaintiff with regard to th e roof the. So, according to the doctrine of proximate cause as articu lated in this case, it still holds that the company was not negligent and the court's finding is supported. There is a second way to look at proximate cause and Palsgraf in light of modern scientific theories. Modem theories postulate that the apparently chaotic phenomenon which are occurring at the station are actually following rules. A determini stic pattern of behavior exists even though it is not readily discerni ble. All of the operative degrees of freedom define a phase space, and phase space analysis may elucidate the system's deterministic behavio ral patterns. Phase space analysis is a tool used to visualize the beh avior of a dynamic system over time. Many dynamic systems generally be have in a stable manner, but intrusions from outside a system can alte r the stability in varying degrees. Depending on the disturbance, the system may return to its original pattern, or may be permanently disru pted, adopting a completely new pattern of behavior. Phase space analy sis provides a second way to look at Palsgraf. In a system made of a t rain station and a train, there are a number of phase space portraits which demonstrate predictable patterns, such as the location of the st ation's platform. Other portraits, such as those that include the move ment of passengers, are never stable. The railway company has a respon sibility to maintain the stable system within safe parameters so that it is not permanently disturbed by outside systems. Because the roof t iles at the train station were loose, they were subject to being distu rbed. The loose tiles created what scientists call a zone of danger, a nd the accident was therefore foreseeable. The railway station did not take the proper precautions, and liability results. Using phase space analysis, Palsgraf would have been resolved as Judge Andrews suggeste d in his dissent, and the train company would have been liable. These same theories and scientific principles can be applied to most proxima te cause tort cases. The appendix following this essay contains exampl es of actual cases decided using these principles.