Property law may be the most eternal of secular law. Its basic precepts and conceptions are largely stable and long settled. An aspect of property law undergoing notable change, however, is the law of landlord and tenant. The most important recent change in landlord-tenant law involves the reversal of responsibility for the quality of leased premises. In place of the tenant's traditional burden of caveat emptor and duty of repair, many courts now recognize an implied warranty of habitability, at least for residential tenancies. These same courts typically reject the traditional doctrine that mutual obligations in leases are "independent," that is, that the tenant's obligations are enforceable by a landlord even when the landlord is in breach. Rather, the landlord's right to rent is made to depend on the landlord's meeting the newly recognized obligations to supply habitable premises.
John A. Humbach, The Common-Law Conception of Leasing: Mitigation, Habitability, and Dependence of Covenants, 60 Wash. U. L. Q. 1213 (1983), http://digitalcommons.pace.edu/lawfaculty/98/.