P: X → Y & not ZP: A → ZP: B → AP: Y and A exist.C: ?

rdavidjr84 July 20, 2019

Y exists

How come their is no explanation for y exists? The conclusion appears to only consider A exists from the last premise. Can you please explain what happened with y exists

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Ravi July 20, 2019

@ricckyd,

Great question. We don't need an explanation for 'Y exists' because
it's a premise. The conclusion actually considers that Y exists
because in order to get this question right, you need to be able to
see what's going on with the contrapositive of the first premise.

X - >Y and not Z

Z OR not Y - >not X

A - >Z

B - >A

Y and A exist.

If A exists, then Z exists. Z existing satisfies the sufficient part
of the contrapositive of the first rule, so we can conclude that X
doesn't exist in addition to Z existing. This is why (D) is right.

Does this make sense? Let us know if you have any other questions!

antariuscaldwell January 5, 2020

Can you explain this problem to me ?

jasminekbond96@gmail.com April 9, 2020

I am a bit confused on this problem. Could you explain it? I am a bit confused as to how to get the conclusion when it says "Y and A exist".

Cothomas25 May 3, 2020

Completely lost with this one

Raechel-Brodsky May 14, 2020

So because Z us necessary to A existing it overrules the first premise??

Raechel-Brodsky May 14, 2020

I think I'm also lost in what rule is necessary to Y's existence? Can you give me the link between B and Y?