## logic question

Prepare for the LSAT or discuss it with others in this forum.
winnatech

Posts: 33
Joined: Tue Dec 18, 2007 10:11 pm

### logic question

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

Posts: 113
Joined: Sun Aug 01, 2010 10:20 pm

### Re: logic question

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

Anaconda

Posts: 605
Joined: Sun Jun 06, 2010 3:51 pm

### Re: logic question

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.

gdane

Posts: 14025
Joined: Sat Sep 26, 2009 2:41 pm

### Re: logic question

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

Posts: 656
Joined: Wed Jul 15, 2009 10:21 pm

### Re: logic question

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.

dub

Posts: 73
Joined: Fri May 21, 2010 9:05 pm

### Re: logic question

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

Posts: 465
Joined: Mon Dec 28, 2009 3:22 pm

### Re: logic question

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

Posts: 69
Joined: Mon Jul 26, 2010 9:28 pm

### Re: logic question

094320

Posts: 4086
Joined: Sat May 16, 2009 5:27 pm

### Re: logic question

..

op-ti

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

### Re: logic question

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?

Dany

Posts: 11559
Joined: Mon Sep 28, 2009 3:00 pm

### Re: logic question

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

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!