Not ALL and Some

[Minnie]

Sorry, I still cannot understandant why As a point of definition Not All is the same as Some Are Not
Thanks

[Claire Horan]

Hi Minnie,

Examples may help! "Some" has slightly different usage in logic than in everyday life.

Not all lawyers are ethical.

That is the same as saying Some lawyers are not ethical.

For the purposes of LSAT, "some" can be defined as "at least 1." And saying "not all" is the same as "at least 1 is not." The opposite of these equivalent statements is "All lawyers are ethical."

Another important thing to note is that because "some" just means "at least one," it INCLUDES "all".

And lastly, because some means "at least one," it's logical opposite is "none".

You can figure out logical opposites by thinking about all the possibilities. For example, "none" and "all" wouldn't include everything, but "none" and "some" would include all the possibilities.

I hope you find this helpful!

[LSAT student]

Hello,

I just finished reviewing logical opposites, and was wondering since "some" and none are polar opposites, does that mean "not some" would always mean "none"? Could "not some" also mean "all"? Is that important for me to understand for the exam?

To check for understanding. Is it correct that "Always" and "never" would be polar opposites? What are the relationships between "sometimes" and "not always", and then "always" and "sometimes"?

[Rachael Wilkenfeld]

Hi LSAT student,

There's some confusion here. Some and none aren't polar opposites, they are logical opposites. The polar opposites are the most extreme ends of a continuum, for example all and none. The term some doesn't really have a polar opposite because it doesn't sit at the extreme end of a continuum.

Since some and none are logical opposites, they need to contain the entire spectrum from 0-100. None is easy. It's represented by 0. Some has to contain the rest of the spectrum from 1-100. That means that some includes the concept of all.

You are correct that always and never are polar opposites (you can also think of them as "all of the time" and "none of the time"). Always and sometimes have the same relationship as all and some; sometimes includes the idea of always.

Sometimes and not always are different. Sometimes is everything from 1-100, but not always can't include always (the 100). It includes everything on our 0-100 spectrum except the always, so it goes from 0-99. Importantly, it includes never, while sometimes does not.

These concepts are tricky, but the are important to understand for the exam.

Hope that helps!

[jdavidwik]

So would the logical opposite of "all", i.e. "not all", include "none"?

[KelseyWoods]

Hi jdavidwik!

Yes, "not all" includes "none." It helps to use numbers, as Rachael does above.

"All" is 100. "Not all" is everything from 0-99. Since "none" = 0, this means that "not all" includes "none."

"None" is 0. "Some" is everything from 1-100. Since "all" = 100, this means that "some" includes "all."

With logical opposites you're essentially dividing everything in the world into two groups. So if my only two groups are "all" and "not all," which group would "none" have to go into? The "not all" group! If my only two groups are "none" and "some," which group would "all" have to go into? The "some" group!

Hope this helps!

Best,
Kelsey

[jdavidwik]

Thank you Kelsey!

I applied that numbering system to the most prevalent LSAT quantity terms and their logical opposites, fitting most into one of two categories, either those with "100" vs. "0-99" or those "1-100" vs. "0" opposition logically. I just have a less-than-full acceptance concerning how to think about one pair of logical opposites; if you have any advice on how to think about this pair it would be greatly appreciated.

This concerns "any" vs. "not every", as per PrepTest 67, S2,Q14, answer choice "E". This is not the correct answer choice, as its negation doesn't significantly weaken the conclusion of the argument, but considering this reminds me of why the phrase "logical negation" is sometimes used when "logical opposite" should be used instead (please advise if in error). Performing the negation test is when the need for logical opposition usually arises. "Mutually exhausting the domain", Powerscore's other way of summarizing the considerations herein, as per https://blog.powerscore.com/lsat/negati ... tatements/ , helps complete my thought here...almost. I can think of "not every" as referring to any number of moieties between 0 and 99, and "any" becomes "any (one)" and occupies spot 100 in this construct. "Not every" is grouped with "not all" and I can see that. "Any" is grouped with "all" and I could just unflinchingly accept that, but I can only seem to accept it as "any (one)" in logical opposition to "not every", and I still do not feel 100% certain about my thinking here. I can accept All, Always and Everywhere as 100 in their logical opposition pairs, but not sure if my "any (one) occupying spot 100" in its construct is the best way to think about that.

[jdavidwik]

Thank you Kelsey!

I applied that numbering system to the most prevalent LSAT quantity terms and their logical opposites, fitting most into one of two categories, either those with "100" vs. "0-99" or those "1-100" vs. "0" opposition logically. I just have a less-than-full acceptance concerning how to think about one pair of logical opposites; if you have any advice on how to think about this pair it would be greatly appreciated.

This concerns "any" vs. "not every", as per PrepTest 67, S2,Q14, answer choice "E". This is not the correct answer choice, as its negation doesn't significantly weaken the conclusion of the argument, but considering this reminds me of why the phrase "logical negation" is sometimes used when "logical opposite" should be used instead (please advise if in error). Performing the negation test is when the need for logical opposition usually arises. "Mutually exhausting the domain", Powerscore's other way of summarizing the considerations herein, as per https://blog.powerscore.com/lsat/negati ... tatements/ , helps complete my thought here...almost. I can think of "not every" as referring to any number of moieties between 0 and 99, and "any" becomes "any (one)" and occupies spot 100 in this construct. "Not every" is grouped with "not all" and I can see that. "Any" is grouped with "all" and I could just unflinchingly accept that, but I can only seem to accept it as "any (one)" in logical opposition to "not every", and I still do not feel 100% certain about my thinking here. I can accept All, Always and Everywhere as 100 in their logical opposition pairs, but not sure if my "any (one) occupying spot 100" in its construct is the best way to think about that.

I just found this in "Plain Language", which is a regular feature of the Michigan Bar Journal, from October 1991, David S. Elder writing:
"One definition of "all" is "any whatever." Webster's Ninth New Collegiate Dictionary (Merriam-Webster, 1984),p 71. In other words, "any" is broad enough to include "all," and "all" can mean any one . Even more convincing is Black's Law Dictionary (6th ed), p 94, which defines "any" as follows:"Some, one out of many; an indefinite number. One indiscriminately of whatever kind of quantity .... '[A]ny' has a diversity of meaning and may be employed to indicate 'all' or 'every'... and its meaning in a given statute depends upon the context and the subject matter of the statute. It is often synonymous with 'either,''every,' or 'all."' (Citations omitted;emphasis added.)"

That sheds light on my question and seems to address what I was finding difficulty in accepting.