Hi all!

I just have a question regrading And + Or in the SC and NC and what happens when you Satisfy the SC through Valid Argument Form #1 and Deny the NC through Valid Argument Form #2. Here is where my thinking is at right now if any of you can correct me please do!!

Or in the Sufficient Condition

Valid Argument Form #1: Satisfying the Sufficient Condition

A or B --> C

Because it is an or statement there are three ways that can you can possibly satisfy the Sufficient Condition and conclude C.

  • A and /B
  • B and /A
  • A and B (Because unless otherwise specified we default to or as inclusive)
  • Valid Argument Form #2: Denying the Necessary Condition

    A or B --> C

    When you deny the Necessary Condition by saying /C you can end up with 3 possibilities.

  • A and /B
  • B and /A
  • /A and /B
  • And in the Necessary Condition

    Valid Argument Form #2: Denying the Sufficient Condition

    A --> B and C

    When you say /B and /C you conclude /A because B and C are jointly necessary they must both be denied.

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    3 comments

    • Friday, May 10 2019

      Valid Argument Form #2: Denying the Necessary Condition

      A or B --> C

      When you deny the Necessary Condition by saying /C you can end up with 3 possibilities.

      A and /B

      B and /A

      /A and /B

      In the above case, when you deny C, you must deny A AND deny B. So your #1 and #2 statements are not correct.

      /C --> [/A AND /B]

      It is also easier to break up OR in the sufficient condition like this:

      A or B --> C

      A --> C

      B --> C

      Therefore, when

      /C --> /A

      /C --> /B

      and if you want to combine the above,

      /C --> [/A AND /B]

      (because AND in the necessary condition can be split)

      Hope this makes sense and let me know if you have questions!

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    • Thursday, May 09 2019

      @drbrown2259 Ah i see thank you so much for the clarification. I just thought that because it was A --> B AND C that it requires that both the Necessary Conditions (B and C) be negated to get /A.

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    • Thursday, May 09 2019

      @99sav99sav106 said:

      Hi all!

      I just have a question regrading And + Or in the SC and NC

      Or in the sufficient condition is sometimes easier mapped as 2 separate conditional statements.

      A --> C , B -->C. Negating C would negate both A and B. With contrapositives of and/or statements you have to change the and/or to the opposite or/and.

      So with that as a rule (De Morgan's Laws from CC), we need to fix up your description of and in the necessary condition.

      A --> B and C. The contrapositive turns into an or in the sufficient conditions, which we can map into two separate conditional statements. /B or /C --> /A. /B --> /A because if A then B and C. /C --> /A because if A then B and C. You don't have to have both B and C negated to get not A.

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