Solving an Invalid Syllogism oai-3 Question

[Daedalus1]

Hi,
I was wondering if anyone could show me why a syllogism of the form oai-3 is invalid.

Thanks

 

[HallsofIvy]

I was hoping someone else would answer this because I have no idea what "oai-3" means!

 

[poutsos.A]

These are the initials of the famous Aristotelean syllogisms:

A; All S is P

E : No S is P

I : Some S is P

O : Some S is not P

Now an OAI-3 IS combination out of the 600 something ,not all of course valid

I think Deadalus1 must not make his question deadalodic and give us the syllogism