Diagramming Challenge!

[scho216]

I have a couple of questions regarding diagramming sentences including conditional reasoning.

1) A if only B --> is this A->B or B->A?
It sounds like B is sufficient for A, but I am not sure since "only if" signifies a necessary condition.

2) A --> B even if C
In this case, is C also a necessary condition for A?
Also, would you diagram it as A-->B and C?
How about the case when it states A-->B although C?

3) A--> B + [C-->D+E]
In this complex sentence, if you want a contrapositive, would it be:
not B OR [C->not D OR not E] --> not A
OR...
not B OR not C --> not A?
(and disregard D and E)

4) How much time do you typically recommend spending diagramming for questions like Must Be True, Cannot be true, etc.?
I think I am sometimes spending too much time diagramming especially if it's complicated, thereby losing time for other questions.

Please help!
Thanks!!

[tommywallach]

Hey Scho,

This is a very epically long question, my friend. I'd recommend you get our book on Logical Reasoning, as it will answer all these questions at great length, which is really what you need. Good luck studying!

(That said, other students are welcome to answer these questions, if you feel like it!)

-t