logic question

winnatech
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Joined: Tue Dec 18, 2007 10:11 pm

logic question

Postby winnatech » Tue Aug 10, 2010 9:39 pm

Hi,

If there is a condition that is "All A are B", does that also mean that "some B are A" as well? Thanks.

stargazin
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Joined: Sun Aug 01, 2010 10:20 pm

Re: logic question

Postby stargazin » Tue Aug 10, 2010 9:45 pm

Yes. It's that "inference ladder" thing. A --> B also means A <--some--> B.

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Anaconda
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Re: logic question

Postby Anaconda » Tue Aug 10, 2010 9:48 pm

Correct.

Ex)

All MLB all-stars are baseball players.

You can infer that some baseball players are all-stars, but you can't imply that ALL baseball players are all-stars.

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gdane
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Re: logic question

Postby gdane » Tue Aug 10, 2010 9:49 pm

You must remember that when you have an If A then B statement, SOME B are A, but not ALL B are A.

If youre confused about conditional reasoning go over that section in the logical reasoning bible and there's a conditional reasoning guide here on TLS that is also helpful.

Good luck!

tamlyric
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Re: logic question

Postby tamlyric » Tue Aug 10, 2010 9:51 pm

Strictly speaking, no. But, assuming that at least one thing is A, then yes. Since LSAC probably doesn't worry about the situation in which nothing is A, I think it's a pretty safe bet that "All As are Bs" entails "Some B is A." So, for example, if all politicians are liars, then at least one liar is a politician--i.e., assuming that there is at least one politician.

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dub
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Re: logic question

Postby dub » Tue Aug 10, 2010 10:22 pm

tamlyric wrote:Strictly speaking, no. But, assuming that at least one thing is A, then yes. Since LSAC probably doesn't worry about the situation in which nothing is A, I think it's a pretty safe bet that "All As are Bs" entails "Some B is A." So, for example, if all politicians are liars, then at least one liar is a politician--i.e., assuming that there is at least one politician.


Right. In LSAT logic, if a word for something exists, that something exists.

lawgod
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Re: logic question

Postby lawgod » Tue Aug 10, 2010 10:37 pm

There could be no A.

My system: Forget the rules and just think about what makes sense.
(easy for me to say, I'll never take another LSAT)

arean.ryan
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Re: logic question

Postby arean.ryan » Wed Aug 11, 2010 3:00 pm

Image

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acrossthelake
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Re: logic question

Postby acrossthelake » Wed Aug 11, 2010 3:15 pm

I just like to think of these in terms of ven diagram worlds.

op-ti
Posts: 128
Joined: Mon Dec 28, 2009 1:36 pm

Re: logic question

Postby op-ti » Wed Aug 11, 2010 3:20 pm

gdane5 wrote:You must remember that when you have an If A then B statement, SOME B are A, but not ALL B are A.

If youre confused about conditional reasoning go over that section in the logical reasoning bible and there's a conditional reasoning guide here on TLS that is also helpful.
Good luck!



Really?

Does anyone have a link to this?

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Dany
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Re: logic question

Postby Dany » Wed Aug 11, 2010 4:01 pm

op-ti wrote:
gdane5 wrote:You must remember that when you have an If A then B statement, SOME B are A, but not ALL B are A.

If youre confused about conditional reasoning go over that section in the logical reasoning bible and there's a conditional reasoning guide here on TLS that is also helpful.
Good luck!



Really?

Does anyone have a link to this?

http://www.top-law-schools.com/conditio ... oning.html

-I don't know if that was the one being referenced, but it's the only one I know of on here.

op-ti
Posts: 128
Joined: Mon Dec 28, 2009 1:36 pm

Re: logic question

Postby op-ti » Wed Aug 11, 2010 4:02 pm

eskimo wrote:
op-ti wrote:
gdane5 wrote:You must remember that when you have an If A then B statement, SOME B are A, but not ALL B are A.

If youre confused about conditional reasoning go over that section in the logical reasoning bible and there's a conditional reasoning guide here on TLS that is also helpful.
Good luck!



Really?

Does anyone have a link to this?

http://www.top-law-schools.com/conditio ... oning.html

-I don't know if that was the one being referenced, but it's the only one I know of on here.


THANK YOU eskimo!




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