In Sullivan et al. v. The Fulton Steam Boat Company, the Supreme Court of the United States heard a case concerning an incident in which a steamboat owned by The Fulton Steam Boat Company collided with another vessel on the Hudson River and caused significant damage to both vessels as well as injury to passengers aboard one of them. At issue was whether or not The Fulton Steam Boat Company could be held liable for damages resulting from its negligence in operating its boat at too high a speed under existing maritime law. In deciding this case, Chief Justice John Marshall wrote that it was necessary to consider "the nature and degree of care" required when navigating such waters, noting that although there may have been no specific regulations governing navigation on rivers like the Hudson at that time, reasonable care must still be taken by those who navigate them regardless of any lack thereof. Ultimately, he found that due to their failure to exercise reasonable caution while operating their vessel on such waters, The Fulton Steam Boat Company should indeed be held liable for damages resulting from their negligence and ordered them accordingly pay compensation for all losses suffered by Sullivan et al., including medical expenses incurred due to injuries sustained during the collision.

In Sullivan et al. v. The Fulton Steam Boat Company, the Supreme Court was asked to decide whether a contract between two parties could be enforced if it violated public policy or law. Chief Justice Marshall wrote the dissenting opinion and argued that contracts should not be enforced when they are contrary to public policy or law because this would encourage people to break laws in order to gain an advantage from their contracts. He further argued that allowing such contracts would lead citizens into dangerous situations where they might unknowingly violate laws without any legal protection against prosecution for doing so. In conclusion, he believed that enforcing such contracts would undermine the rule of law and ultimately cause more harm than good by encouraging illegal behavior among citizens who may not even know what is prohibited by statute or common law.