June 2010 LSAT Section 5 Question 18

Based on the passage, it can be concluded that the author and Broyles-González hold essentially the same attitude toward

ankita96 on May 29, 2020

All statements Reversal

In quantifier statements, for example All statements, does the reversal apply the same rule as other conditional statements. I.e. when we reverse an all statement we get a some statement, so do we also negate the statement variables. This question is with reference to Example 2 option 3. WLG-some- not CNG is what the option says. Our deduction was that CNG - WLG which on reversal would be WLG-some-CNG, in this reversal is it not supposed to negate? and does that apply to all quantifier statements

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Victoria on May 29, 2020

Hi @ankita96,

When you reverse quantifier statements, you do not negate. You only have to both reverse and negate when you are diagramming the contrapositive of a S&N statement.

In this example, we can conclude two things from our deduction (CNG --> WLG):

(1) CNG --> WLG
Not WLG --> Not CNG

(2) CNG --> WLG
WLG - some - CNG

For conclusion (2), if all countries with corrupt national governments have weak local governments, then we can also conclude that some countries which have weak local governments will also have corrupt national governments. Unlike in a S&N statement, this statement is true if we do not negate the variables.

Overall:

(1) Always reverse and negate S&N statements
(2) Exception to Rule 1: you can simply reverse 'all' statements if you replace 'all' with 'some'
(3) 'Some' statements are reversible - you do not need to negate
(4) 'Most' statements are reversible if you replace 'most' with 'some' - you do not need to negate.

Hope this is helpful! Keep up the good work and please let us know if you have any further questions.