A New Argument for deductio ex mercede

In his book Landlords and tenants in Imperial Rome and in a number of articles, B.W. Frier has advocated the existence of a legal remedy which functioned in the context of urban lease in classical Roman law. This remedy, called deductio ex mercede, was seemingly only available to tenants of urban property. It was essentially a form of legalised self-help that arose during the Republic and which enabled urban tenants unilaterally to deduct an amount of rent when undisclosed circumstances.