Salvatore argues that, because demand for antique ivory is higher than supply, people who don’t care about endangered species have to buy new ivory even if they wanted antique ivory. In order to stop these people from buying new ivory, people who care about endangered species should therefore not buy any ivory at all.

The argument’s premises explain why not buying any ivory might reduce the demand for new ivory. Right now the demand for ivory is too high, so if it decreased then people who don’t care about endangered species could buy antique ivory instead of new ivory. It then, however, moves to a conclusion about what people who care about endangered species should do - they should take steps to reduce the demand for ivory. We’re therefore looking for some principle that explains why people who care about endangered species should try to make sure that other people don’t buy new ivory.