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Tuesday, Jul 21, 2020

Formal Logic help

Can someone please help me diagram and understand the inferences made from these statements?

Some As are Bs.

All Cs are Ds

No Bs are Cs.

Here is what I have so far.

AsomeB—-> ~C

~D—->~C

Inference: Asome~C

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5 comments

  • Wednesday, Jul 22, 2020

    Here is how you do it:

    If we have these two conditional statements:

    X —> Y

    Z —> Y

    We can’t infer anything...

    However, if we take the contra-positive of those two conditional statements, we get the following:

    ~Y —> ~X

    ~Y —> ~Z

    From there we can infer that ~X (—S—) ~Z

    The reason behind that is the following: ~X and ~Z must share some common-ground or, as JY says, some interception because ~Y is brought into ~X and ~Z...

    I hope this helps - good luck studying!

    1
  • Tuesday, Jul 21, 2020

    Some As are Bs: As (---S---) Bs

    All Cs are Ds: Cs ---> Ds

    No Bs are Cs: Bs ---> ~Cs

    Linking them will look something like this:

    As (---S---) Bs ---> ~Cs

    ~Ds ---> ~Cs

    (I can't find a way to connect Bs and ~Ds to ~Cs, but if you are writing this down, you should connect them...)

    Anyway, the inferences are:

    As (---S---) ~Cs

    ~Bs (---S---) Ds

    I hope this helps!

    1
  • Friday, Jul 24, 2020

    Of course, let me know if you have any other questions.

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  • Thursday, Jul 23, 2020

    @fyepes582 Thank you so much!!

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  • Wednesday, Jul 22, 2020

    @fyepes582 Thank you for the reply. How did you make the inference ~B (--s--) D? I am having trouble making that inference.

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