A<---B some C
it can be inferred to C some A
but why can't
A some B <----C
have an inference of C some A
if the somes can be reversed why can't this be true. To me the book didn't offer a good explanation. Can anyone explain this?
Explanation needed-LR Bible-inferences Forum
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Cambridge LSAT
- Posts: 257
- Joined: Mon Aug 24, 2009 3:26 pm
Re: Explanation needed-LR Bible-inferences
From this information alone, we don't know for sure that C and A must overlap. For example, this hypothetical diagram is compatible with the second scenario you presented, but it contradicts the A some C inference.
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timmydoeslsat
- Posts: 148
- Joined: Wed Aug 03, 2011 2:07 pm
Re: Explanation needed-LR Bible-inferences
A some B ---> C
I can validly infer that A some C. I know that some A's are B's and that every B is a C, so I must have A with some C's too.
A ---> B some C
I cannot validly infer that A some C. I know that every A is a B. But I only know that some B's are C's. For instance, lets say that there is one A in existence and that there are 50 B's in existence. I can have that single A be a B, yet have the other B's be with C's and not the single A.
A
BBBBBB
.....CCC
I can validly infer that A some C. I know that some A's are B's and that every B is a C, so I must have A with some C's too.
A ---> B some C
I cannot validly infer that A some C. I know that every A is a B. But I only know that some B's are C's. For instance, lets say that there is one A in existence and that there are 50 B's in existence. I can have that single A be a B, yet have the other B's be with C's and not the single A.
A
BBBBBB
.....CCC
