The author uses the word "immediacy" (line 39) most likely in order to express
Sylvieon May 26, 2020
Question #8
In answer B for question 8, why is "balloons" not a sufficient condition for "birthday party"? Is the presence/absence of balloons not the sufficient condition for determining the party?
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"Balloons" is the necessary condition for "birthday party." We know that Jenny will have lots of balloons at her birthday party.
Therefore, if it is Jenny's birthday party, then there will be lots of balloons.
The presence of balloons is not sufficient for it to be Jenny's birthday party as it is not necessary for it to be Jenny's birthday party for there to be lots of balloons. Rather, "balloons" is the necessary condition because it cannot be Jenny's birthday party without the balloons.
Hope this is helpful! Please let us know if you have any further questions.
Sylvieon May 27, 2020
Hi @Victoria,
Thanks, that does help. I guess I was projecting beyond the terms of the question stimulus.
I do have some additional questions. First, can you please explain to me what it means when the certain premises are underlined -- such as in the Argument Completion and Missing Premise Drills that accompany this lesson? E.g.:
P: X -> Y
P: not X -> C (underlined)
C: ? (also underlined, though I'm assuming this is because it's the conclusion?)
As I've been working through these assignments, I keep coming across problems where I get the correct answer but in contrapositive form (or vice versa). Many of them seem to feature premises that are underlined, so I'm wondering if I'm missing something.
More broadly though, if the positive and contrapositive are logically equivalent, would these answers still be correct? It seems to me that having multiple choice answers, as on the test, might solve the problem, since the drills in question are in flashcard form (not multiple choice). Just want to make sure I'm doing these right!
Thanks so much!!
Sylvie
Sylvieon May 28, 2020
Just replying again in the hopes of getting a follow-up response. I think I resolved the underlining issue (separating premises from conclusions and underscoring the latter?) but would still very much appreciate confirmation that contrapositive is just as correct as the positive formulation in the absence of multiple choice. Thanks @Victoria (or anyone else)!
shunheon May 30, 2020
Hey @Sylvie, yes, the contrapositive statement is logically equivalent to the original, and so those types of answers would be correct. If you're expecting A-->B and you see ~B-->~A, you can reasonably expect that to be the correct answer.
