Treating S w/ N as must be trues

Emil gave an office hour on how he thinks S w/ N should be approached as must be trues. You should ask "what must the author believe to derive this conclusion?" I've been using that strategy with success but this question in particular highlights where that strategy is more effective fulfilling the two criteria: 1. Does it strengthen? 2. If negated, does the argument collapse? If you negate C, it takes a while to understand if it collapses the argument or has no effect. You can easily talk yourself into C collapsing the argument. If you look at D, however, and ask "must the author believe this?" the answer is unequivocally yes. If you ask the same thing about C, you can look at the conclusion and see how weak it is to realize the author does not necessarily have to believe C to be true to derive his conclusion.