It looks like you're new here. If you want to get involved, click one of these buttons!

- 30.9K All Categories
- 26.2K LSAT
- 16K General
- 28 Sage Advice
- 4.9K Logical Reasoning
- 1.3K Reading Comprehension
- 1.6K Logic Games
- 73 Podcasts
- 189 Webinars
- 6 Scholarships
- 192 Test Center Reviews
- 1.8K Study Groups
- 100 Study Guides/Cheat Sheets
- 2.3K Specific LSAT Dates
- 0 February 2024 LSAT
- 0 January 2024 LSAT
- 8 November 2023 LSAT
- 25 October 2023 LSAT
- 9 September 2023 LSAT
- 33 August 2023 LSAT
- 26 June 2023 LSAT
- 4.7K Not LSAT
- 3.8K Law School Admissions
- 10 Law School Explained
- 11 Forum Rules
- 539 Technical Problems
- 267 Off-topic

pfjddream
Free Trial Member

I am confused between the difference of these two forms of conditional logic

not A -> B

not B -> A

versus

A -> not B

B -> not A

Do both forms above really mean either or, but not both?

In one of the games explanations, I remember coming across a point that starting with a negative term as the sufficient condition, meaning where the absence of a sufficient condition guarantees a necessary condition is somehow different than starting with a positive term for the sufficient where the presence of a sufficient condition guarantees the necessary condition. BUT I am having trouble seeing if there is a difference in the meaning of the above two forms and hat kinds of inference I can make from them.

Can someone please clarify this? I am really confused.

Thanks,

Pamela

not A -> B

not B -> A

versus

A -> not B

B -> not A

Do both forms above really mean either or, but not both?

In one of the games explanations, I remember coming across a point that starting with a negative term as the sufficient condition, meaning where the absence of a sufficient condition guarantees a necessary condition is somehow different than starting with a positive term for the sufficient where the presence of a sufficient condition guarantees the necessary condition. BUT I am having trouble seeing if there is a difference in the meaning of the above two forms and hat kinds of inference I can make from them.

Can someone please clarify this? I am really confused.

Thanks,

Pamela

## Comments

the bottom means you have A but not B, B but not A, or Neither A or B

So the first one is either or (possibly both) and the second one is either or but not both