Contrapositive of 'some' statements

[brandonhsi]

Can you take a contrapositive of a "some" statement? As far as I know, one shouldn't do that until I try to find more about "contrapositive."

http://www.philosophypages.com/lg/e07b.htm

According to the information from the link above, you can't take a contrapositive of a "I proposition: Some S are P." However, there is a contrapositive of "O proposition: Some S are not P."

Also, the way it takes the contrapositive of "Some S are not P" is kind of weird. I thought it should be "Some not (not P) are non S", but it is not the case here. It left the "not" alone, and flip/negate P and S. I always believe "not P" is "non P." Has I been wrong all the time?

I believe it is more than I should know for the LSAT, but anyone could help me here? Thanks!

[maryadkins]

If we know some S are P, you're right, we don't know that some S are not P. All S could be P. But we do know that some P are S.

If we know some S are not P, we know that some not Ps are S. That's all. We don't know if some S are P, or anything about the not S's.

Don't think about "some" statements as contrapositives and flipping. It doesn't work and gets confusing. There are great "some" drills and explanations in the Manhattan LSAT Logical Reasoning Guide"”I'd learn from there.