Formal logic question... Forum

[klikme]

I'm preparing lsat with Powerscore. Here I have a question regarding formal logic.

Some A's are B's.
No B's are C's.
All C's are D's.

Diagram : A some B <-/->(double not arrow) C -> D
Inferences : 1. A some not C
2. D some not B (according to the Bible)

Question : Isn't the inference "A some D" possible?
(For in the diagram "A some B <-/-> C" can be replaced with the inference 1 "A some not C", then this would make "A some not C -> D" and again "A some D".)

Thanks.

[Nulli Secundus]

A some not C
C -----> D

Since the second part of first inference is "not C" and first part of second inference is "C" you cannot combine them. HTH.

[d34d9823]

A some not C
C -----> D

Since the second part of first inference is "not C" and first part of second inference is "C" you cannot combine them. HTH.

Yeah, some As being Bs doesn't preclude all As being Bs.

[klikme]

Thanks guys