Question on Conditional Reasoning

[LSATUSERNAME3]

Thank you

[Jeremy Press]

Hi LSAT,

First of all, understand that "or" in LSAT conditional rules is always inclusive (including in the contrapositive example you cited) unless the given rule explicitly says otherwise. That means any time I see an "or" I assume both things could happen simultaneously. If the "or" is on the sufficient side of the arrow, that means both of the conditions together could occur, which would trigger the occurrence of the necessary condition. If the "or" is on the necessary side of the arrow, this means the occurrence of the sufficient condition could trigger the occurrence of both of the necessary conditions (so long as the rule doesn't explicitly say "not both").

Imagine this real world example: "If you become President of the United States, you must be at least 35 years old and a natural born citizen of the United States" (President 35 + natural born citizen). The contrapositive would be, "If you are not at least 35 years old or you are not a natural born citizen of the United States, then you cannot become President of the United States" (~35 or ~natural born citizen ~President).

So what about someone who is only 25 years old AND is not a natural born citizen of the United States? Can they become President? Definitely not. That's what it means for the "or" to be inclusive.

Does that clarify it? Hopefully so!

Jeremy