Ha! It doesn’t actually follow from the negation of the conclusion of Singer’s argument that you’re not obligated to save the drowning child, though: the antecedent of that conclusion is a conjunction, of which ‘I am obligated to save the drowning child’ is one of the conjuncts.
ETA:...I now see that what I’m saying is that the quote in the parent is wrong: he doesn’t actually argue that these two are equivalent. You also need to accept (maybe in addition to others) the premise that if you’re obligated to save the drowning child, you’re obligated to save a child who isn’t in immediate danger in your immediate presence.
Ha! It doesn’t actually follow from the negation of the conclusion of Singer’s argument that you’re not obligated to save the drowning child, though: the antecedent of that conclusion is a conjunction, of which ‘I am obligated to save the drowning child’ is one of the conjuncts.
ETA:...I now see that what I’m saying is that the quote in the parent is wrong: he doesn’t actually argue that these two are equivalent. You also need to accept (maybe in addition to others) the premise that if you’re obligated to save the drowning child, you’re obligated to save a child who isn’t in immediate danger in your immediate presence.