Answer: Fungibilty problem
Explanation: The concept of internalizing extercost could best be explained as policies which intends to balance and shift cost or effect of external factors on the masses. As mentioned in the question abive, a concept of internalizing external cost is the use of fiscal policies in the associating property rights to goods which one does not even own. The concept of fungibilty preaches equality in the value of exchaved goods or asset. This concept is trampled upon when individuals have to bear and pay for cost which they did not incur explicitly.