## Formal Logic Question

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sottovoce

Posts: 15
Joined: Tue Nov 13, 2012 8:43 am

### Formal Logic Question

Hey guys,

This might be a really basic question and I feel dumb here. But on one of the questions in the Logic Reasoning Bible it asks you to give inferences and diagrams of certain premises.

So it says:
Some T's are U's.
All U's are V's.
All T's are S's.

Final diagram I got right:
S <--- T some U --> V

However, one of the inferences is S some V!

I thought that is not necessarily true.

Let's say that there are two components of T, half which are made out of S (some S's are T's) and half of which are NOT made out of S. We know that some T's are U's. But let's say that the T's that ARE U's are composed only of the half that is not S's! This would mean, even though all U's are V's, there is no connection between U and S, and in this situation exactly 0 S's are V's.

I am probably have a flaw in my logic. Please let me know. Thanks.

RZ5646

Posts: 2391
Joined: Fri May 30, 2014 1:31 pm

### Re: Formal Logic Question

What is powerscore's inference? Some V's are S's? Or some S's are V's?

sottovoce

Posts: 15
Joined: Tue Nov 13, 2012 8:43 am

### Re: Formal Logic Question

Some S's are V's. S some V.

CardozoLaw09

Posts: 2183
Joined: Sat Aug 28, 2010 1:58 pm

### Re: Formal Logic Question

Final diagram I got right:
S <--- T some U --> V

At least one V is a U, and at least one U is a T, and all T's are S's, so there could be one V that's also an S aka V some S or S some V

sottovoce

Posts: 15
Joined: Tue Nov 13, 2012 8:43 am

### Re: Formal Logic Question

CardozoLaw09 wrote:
Final diagram I got right:
S <--- T some U --> V

At least one V is a U, and at least one U is a T, and all T's are S's, so there could be one V that's also an S aka V some S or S some V

Thanks so much. I am trying to get it in a little bit more conceptual terms. Can you explain to me why my scenario doesn't make sense?

RZ5646

Posts: 2391
Joined: Fri May 30, 2014 1:31 pm

### Re: Formal Logic Question

Ok you made a mistake right at the beginning: "Let's say that there are two components of T, half which are made out of S (some S's are T's) and half of which are NOT made out of S."

That contradicts "All T's are S's." You can't have a T that is a non-S, since we're told that every T is an S.

Basically since every T is also an S, you can just substitute S for T (though not the other way around). Same thing with U and V. So when you read "some T is U," you can make that "some S is V."

You can also look at it with Venn diagrams

or just regular non-powerscore formal logic

NL2424

Posts: 1283
Joined: Wed Dec 24, 2014 1:12 pm

### Re: Formal Logic Question

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Last edited by NL2424 on Fri Jul 10, 2015 10:22 pm, edited 1 time in total.

Rook

Posts: 20
Joined: Thu Dec 18, 2014 4:52 pm

### Re: Formal Logic Question

my inferences are: some t's are v's, some u's are s's, some v's are s's...

are these correct?