Property theorists typically conceptualize property as a strict liability regime. Blackstone characterized property as “that sole and despotic dominion which one man claims and exercises over the external things of the world, in total exclusion of the right of any other individual in the universe.” In more modern terms, property represents what Henry Smith has called an “exclusion strategy”: property law delegates decisions about resource use to an owner, who “is responsible for deciding on and monitoring specific activities with respect to the resource.” Any interference with the owner’s property right in itself gives rise to a legal claim by the owner. The usurper’s excuses for the interference are irrelevant and do not serve as defenses.
The prevailing conception of property is one of clear boundaries, easily and inexpensively ascertainable by owners and potential users. Within that conception, a strict liability regime makes considerable sense: it delegates control over resource use to owners, reducing the need for courts and potential resource users to educate themselves about the value of competing resources. At the same time, strict liability imposes no hardship on encroachers or infringers. An encroacher or infringer only uses a neighbor’s rights because he (unlike the paradigmatic tortfeasor) derives economic benefit from those rights. The gains from use of the owner’s rights provide a fund from which the encroacher can compensate the owner for his losses. If property boundaries were always clear, however, both strict liability and negligence regimes would generate identical outcomes. If a potential resource user could costlessly determine which rights he needed and who owned those rights, the user would act negligently—if not intentionally—whenever he encroached on an owner’s rights.
This Article argues that, in cases where ascertaining the scope of boundaries is costly, property law should, and sometimes does, make use of negligence principles. Current doctrine does not directly incorporate the law of negligence into property law. Instead, property law has developed surrogates for negligence-based liability rules. These surrogate rules protect the interests of a usurper who took reasonable care before investing in a property interest he did not own—the same interests a negligence rule would protect. Thus, although explicit discussions of negligence rarely find their way into property law opinions, issues of fault do play a significant role in property cases and perhaps should play a bigger, more explicit role in the future.