Taking externalities into account isn&#x27;t hindering others, since the externality is by definition an unwanted imposition pf costs on a third party that didn&#x27;t exist prior to the economic activity that generated it. I fail to see how this is different from an unpaid bill, and Nobel laureate Ronald Coase has rather convincingly argued* that the costs of mitigation in advance or in arrears ends up being the same, but that the transaction costs of enforcing property rights against externalities are a sufficient barrier to many pollutees that polluters are often willing to gamble on others&#x27; inability to adequately enforce their rights and pocket the resulting savings.<p>* in <i>The Problem of Social Cost</i>, an unusually readable essay for the field of economics.