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Wednesday, Oct 21 2015

pt 45 s1 q 21

I have a question on how the video comes to the contrapositive of the answer choice.

"there are many records of major meteor impacts that do not seem to have been followed by mass extinction"

in the stimulus

becomes

""...then all major meteor impacts would be followed by mass extinction"

I understand we need

P ---> -CCL

or

CCL---->-p

And that this is to be P3. But how is all the contrapositive of many? Many could potentially be All. Shouldn't the right answer here be not many aka none, no, etc?

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4 comments

  • Wednesday, Nov 04 2015

    We need to negate some are -not-.... which is "all are".

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  • Wednesday, Nov 04 2015

    I'm unclear how negation of

    Major Meteor Impacts – some-

    becomes

    Major Meteor Impacts

    This is saying that the negation of some is all. I don't see the video you linked answering that. Some can include all. Ie. Some days it rains. What is the negation of this. All days it rains or not some days it rains. I believe it is the later, not some, and not some = it never rains. How can the negation of it rains some days be it rains all days? It is logically inconsistent.

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  • Tuesday, Nov 03 2015

    “There are many records of major meteor impacts that do not seem to have been followed by mass extinction.” Logically written:

    Major Meteor Impacts – some-> /Followed By Extinction

    When we negate, becomes:

    Major Meteor Impacts --> Followed By Extinction

    Ac(A) says logically: CCL --> (MMI --> FBE)

    I believe what it says in English is, “If there is a consistent causal link then Premise 3 is incorrect.”

    Try referring to this as well: http://classic.7sage.com/lesson/the-negation/

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  • Tuesday, Nov 03 2015

    Bump could someone answer?

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