Basic Diagram Question

BroccoliBroccoli Core Member
edited August 2018 in Logical Reasoning 352 karma

Can you solve this or is this invalid

A - (some) - B
B - (all) - c

Comments

  • Tim HortonsTim Hortons Alum Member
    389 karma

    This is a valid argument form because the existential quantifier precedes the universal quantifier. When chained up, it follows that: A ←some→ B → C = A ←some→ C.

    A while ago, back when I was CCing, I put together this master list of all the valid and invalid argument forms and the "rules" that accompany each type. I figure you might find it helpful.
    (Note: on this list, your question pertains to Valid Form 4)

    The VALID Forms (100% Certainty)

    Universal Causation
    Rule: The only valid inference that can be made from a universal causal relationship is its contrapositive

    Form 1: Sufficient/Necessary (A → B + X is A = X is B )
    Form 2: Contrapositive of Form 1 ( A → B + X is /B = X is /A)
    Form 3: Sufficient/Necessary Extension ( A → B → C = A → C)

    Chain Inferences
    Rule: The existential quantifier must precede the universal quantifier.

    Form 4: Some/All/Some ( A ←some→ B → C = A ←some→ C)
    Form 5: Most/All/Most (A ‑most→ B → C = A ‑most→ C)

    Same “Sufficient” Variable
    Rule: Both premises have to share the same (let’s call it ‘sufficient’) variable.

    Form 6: All/All/Some ( A → B + A → C = B ←some→ C)
    Form 7: All/Some/Some ( A → B + A ←some→ C = B ←some→ C)
    Form 8: All/Most/Some ( A → B + A -most→ C = B ←some→ C)
    Form 9: Most/Most/Some ( A -most→ B + A -most→ C = B ←some→ C)

    The INVALID Forms (Not 100% Certainty)

    Universal Causation
    Rule: The only valid inference that can be made from a universal causal relationship is its contrapositive.

    Form 1: Reversing i.e. triggering the necessary ( A → B + X is B ≠ X is A)
    Form 2: Negating i.e. negating the sufficient ( A → B + X is /A ≠ X is /B)

    Inference Chains
    Rule: The existential quantifier must precede the universal quantifier, also implying that a UQ has to be present in the chain.

    Form 3: All/Some Chain (A → B ←some→ C ≠ A ←some→ C)
    Form 4: All/Most Chain (A → B -most→ C ≠ A -most→ C)
    Form 5: Some/Some (A ←s→ B ←s→ C ≠ A ←s→ C)
    Form 6: Most/Most (A -m→ B -m→ C ≠ A -m→ C or A ←some→ C)

    Same “Sufficient” Variable
    Rule: Just no.

    Form 7: Some/Some (A ←some→ B + A ←some→ C ≠ B ←s→ C

  • BroccoliBroccoli Core Member
    352 karma

    @"Tim Hortons" Wow this is amazing. Thank you so much

  • Tim HortonsTim Hortons Alum Member
    389 karma

    @Broccoli180 No problem, happy to help!

  • LCMama2017LCMama2017 Alum Member
    edited August 2018 2134 karma

    @BinghamtonDave I think this is the post you may have seen. Its a great list. I'm going to print it out. Thanks @"tim hortons"

  • btownsqueebtownsquee Alum Member
    1207 karma

    This is valid.

    Whenever I'm confused, I think about JY's bucket method.

    What if there are a whole bunch of As and just one is B. All Bs are Cs. So that means that one A is also C. Therefore we can validly conclude that A some C.

  • BroccoliBroccoli Core Member
    edited August 2018 352 karma

    Thank you. I'll watch bucket method video again.

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