Logical Negation

User avatar
EyeBeeM
Posts: 57
Joined: Tue Jun 10, 2008 12:34 am

Logical Negation

Postby EyeBeeM » Sat Jul 05, 2008 3:07 pm

I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.
Last edited by EyeBeeM on Sat Jul 05, 2008 3:11 pm, edited 1 time in total.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:13 pm

I just finished the Powerscore class and took the June LSAT and they explain it the same way you just did. You are correct in your assessment and so is Powerscore...

User avatar
EyeBeeM
Posts: 57
Joined: Tue Jun 10, 2008 12:34 am

Re: Logical Negation

Postby EyeBeeM » Sat Jul 05, 2008 3:17 pm

btaylor62000 wrote:I just finished the Powerscore class and took the June LSAT and they explain it the same way you just did. You are correct in your assessment and so is Powerscore...


I'm confused...how can we both be right.

In PS's defense they say that 'will not' is actually the polar opposite, not the logical opposite...but they are in practice acceptable.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:20 pm

EyeBeeM wrote:
btaylor62000 wrote:I just finished the Powerscore class and took the June LSAT and they explain it the same way you just did. You are correct in your assessment and so is Powerscore...


I'm confused...how can we both be right.

In PS's defense they say that 'will not' is actually the polar opposite, not the logical opposite...but they are in practice acceptable.


I am saying that you have correctly defined logical negation but incorrectly stated how powerscore defines it. There is a difference between opposite and polar opposite.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:22 pm

bobina wrote:Do you ever even use polar opposites on the LSAT? Why in God's name does PS talk about polar opposites and not merely logical opposites?


They explain both.

User avatar
EyeBeeM
Posts: 57
Joined: Tue Jun 10, 2008 12:34 am

Re: Logical Negation

Postby EyeBeeM » Sat Jul 05, 2008 3:23 pm

btaylor62000 wrote:
EyeBeeM wrote:
btaylor62000 wrote:I just finished the Powerscore class and took the June LSAT and they explain it the same way you just did. You are correct in your assessment and so is Powerscore...


I'm confused...how can we both be right.

In PS's defense they say that 'will not' is actually the polar opposite, not the logical opposite...but they are in practice acceptable.


I am saying that you have correctly defined logical negation but incorrectly stated how powerscore defines it. There is a difference between opposite and polar opposite.


I understand how PS defines it. I just don't see why they would substitute a polar opposite just because it's generally acceptable. I agree with bobina, not sure what the value of a polar opposite would be in these LRs.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:32 pm

EyeBeeM wrote:I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.


"Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance." THIS IS NOT HOW POWERSCORE WOULD DEFINE OPPOSITE... Where are you getting your powerscore info from. If it is the LR bible you are mistaken in your interpretation... they might give that as an example of what we would commonly think of as opposite and then go on to explain the logical opposite..

User avatar
EyeBeeM
Posts: 57
Joined: Tue Jun 10, 2008 12:34 am

Re: Logical Negation

Postby EyeBeeM » Sat Jul 05, 2008 3:44 pm

btaylor62000 wrote:
EyeBeeM wrote:I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.


"Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance." THIS IS NOT HOW POWERSCORE WOULD DEFINE OPPOSITE... Where are you getting your powerscore info from. If it is the LR bible you are mistaken in your interpretation... they might give that as an example of what we would commonly think of as opposite and then go on to explain the logical opposite..


No, I'm not mistaken at all. Open up the LRB go to page 271 and look at question 5. I used vaccinations, they talked about organic farming.

They basically said 'this farming method promotes resistance to pest attacks'. And they gave the opposite as 'this farming method does not promote resistance to pest attacks'.

Look it up if you're so skeptical.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:49 pm

EyeBeeM wrote:
btaylor62000 wrote:
EyeBeeM wrote:I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.


"Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance." THIS IS NOT HOW POWERSCORE WOULD DEFINE OPPOSITE... Where are you getting your powerscore info from. If it is the LR bible you are mistaken in your interpretation... they might give that as an example of what we would commonly think of as opposite and then go on to explain the logical opposite..


No, I'm not mistaken at all. Open up the LRB go to page 271 and look at question 5. I used vaccinations, they talked about organic farming.

They basically said 'this farming method promotes resistance to pest attacks'. And they gave the opposite as 'this farming method does not promote resistance to pest attacks'.

Look it up if you're so skeptical.



OK... You win... congrats.

User avatar
EyeBeeM
Posts: 57
Joined: Tue Jun 10, 2008 12:34 am

Re: Logical Negation

Postby EyeBeeM » Sat Jul 05, 2008 3:51 pm

btaylor62000 wrote:
EyeBeeM wrote:
btaylor62000 wrote:
EyeBeeM wrote:I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.


"Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance." THIS IS NOT HOW POWERSCORE WOULD DEFINE OPPOSITE... Where are you getting your powerscore info from. If it is the LR bible you are mistaken in your interpretation... they might give that as an example of what we would commonly think of as opposite and then go on to explain the logical opposite..


No, I'm not mistaken at all. Open up the LRB go to page 271 and look at question 5. I used vaccinations, they talked about organic farming.

They basically said 'this farming method promotes resistance to pest attacks'. And they gave the opposite as 'this farming method does not promote resistance to pest attacks'.

Look it up if you're so skeptical.



OK... You win... congrats.


Ha, no congrats needed. This isn't about winning a contest. It's about understanding.

btaylor62000
Posts: 11
Joined: Tue Feb 19, 2008 2:46 pm

Re: Logical Negation

Postby btaylor62000 » Sat Jul 05, 2008 3:53 pm

You are correct after I referenced my book :-( The class and class material didn't describe it that way. :roll:

agibson6
Posts: 9
Joined: Wed May 07, 2008 12:06 pm

Re: Logical Negation

Postby agibson6 » Sat Jul 05, 2008 4:23 pm

Does anyone have a good example where this distinction matters in LR? I've often wondered, when negating assumptions answers, if there's a time where using a polar opposite would make you miss the answer.

Using the example, say "Vaccinations promote disease resistance." is the correct answer and the assumption that the author makes. Saying vaccinations DO NOT and vaccinations MAY NOT NECESSARILY will both equally weaken the argument significantly to expose this to be the right answer. I suppose it comes down to whether or not negating a wrong answer choice with a polar opposite could weaken the argument just as significantly and thereby confuse which answer "is best." Thoughts?

EastBay Jose
Posts: 3
Joined: Sat Jun 28, 2008 2:15 am

Re: Logical Negation

Postby EastBay Jose » Sat Jul 05, 2008 5:28 pm

1. "I know for certain that vaccinations promote disease resistance."
2. "I do not know for certain that vaccinations promote disease resistance."

These two statements are opposites of a sort; they're opposite with respect to degree of certainty. The first statement is certain of the truth of a claim. The second statement allows for the possibility that the claim may be absolutely true, but is not certain.

(EyeBeeM: it may be helpful for you to notice that, in regard to the truth of whether vaccinations promote disease resistance, the second statement isn't "0-99" on your scale, it's "0-100.")

3. "Vaccinations promote disease resistance."
4. "Vaccinations do not promote disease resistance."

These two statements are also opposites of a sort. They're equally certain of the truth of two opposite claims.

For the purpose of testing a choice in an assumption question, hypothetically negating either the certainty or the truth of the choice will work:
"What if we weren't certain that this choice was true?"
"What if we knew for certain that this choice wasn't true?"

But doing it the second way will make the right answer jump out more clearly, so that's the best way to do it.

For the purpose of negating the conditions in a conditional statement to get the contrapositive, it depends how the conditional statement is phrased: if it's phrased as a certainty, negate the certainty; if it's phrased as a truth, negate the truth. For example:
if you're certain that X is true, then you must do Y
if you didn't do Y, then you weren't certain that X was true


if X is true, then you must do Y
if you didn't do Y, then X wasn't true

EpyonBlood
Posts: 3
Joined: Fri Jun 25, 2010 1:15 am

Re: Logical Negation

Postby EpyonBlood » Fri Jun 25, 2010 1:29 am

EyeBeeM wrote:I like drawing out these diagrams

0-1----- ... ------99-100

If something happens All the time it is at 100. The opposite would be 0-99, meaning it could happen Not All of the time.

If something happens None of the time it is at 0. The opposite would be 1-100 meaning it happens Some of the time.

So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.

According to PS the opposite of Will is Will Not. But wouldn't Will Not be 0 on the scale, meaning it never happens.

Can someone explain how Will Not covers 0, something never happening and 1-99, something happening sometimes?

Edit: in one example they say 'will not' and 'might not' are equivalent. I disagree, 'might not' makes sense to me as covering 0-99, 'will not' still seems like it's only covering 0.

Edit 2: Another example

Vaccinations promote disease resistance.
PS would say the opposite is Vaccinations do not promote disease resistance. I would say the opposite would be Vaccinations might not promote disease resistance.



Ok...here's my spin on this topic. Whenever you mention the diagram and reference that something that happens all of the time = 100, and something that does not happen all the time is 0-99, you are using time as your base of reference. The same can be applied to the "Will" and "Will Not" situation.

If you constrain the definition of something that "will" happen to now, or any defined period of time, then clearly the logical negation of that would most fittingly be that something "will not" happen [insert previously defined time frame].

Also, in your initial conclusion you draw from your observation,

EyeBeeM wrote:So if we say something will happen we're saying it is inevitable, so it is a hundred. Its opposite must be 0-99 then, which would mean it could happen or it could not happen - it just can't always happen.


The scale value of "will not", 0, is inclusive of the 0-99, as well as coincides with your statement of "it just can't always happen". When something "will not" happen, because it is inclusive of the scale 0-99, it has to be a logical negation.

One could further argue that there could be multiple negations to one logical premise. As you mentioned previously, "it could happen or it could not happen" -- these could pose as two negations of the one "will". Something never happening and something not always happening are two separate constraints on their own, yet both pose as a logical negation to something that "will" happen.

Hope this helps! Any thoughts? Anybody concur or disagree?

Thanks.




Return to “LSAT Prep and Discussion Forum”

Who is online

Users browsing this forum: Baidu [Spider], dontsaywhatyoumean and 2 guests