Either/or Statements

[lizk89]

P. 143: ``Either John or Jack will attend the party.``

The proper diagram according to the text is: No jack John. And no John Jack.

Can it also be stated in this form: Party Jack or John.
If no Jack and no John no party.

Please let me know.

[Steve Stein]

Hi,

Really interesting question. If there were some other factor in the game that allowed for the possibility of no party, then your diagram would be fine.

Otherwise, I would avoid changing the statement like that, because the rule, as stated, does not allow for the possibility of "no party."

In a scenario such as the one you brought up, generally the focus should be placed on the variables under discussion (in this case, Jack and John), as opposed to the event they are involved in (in this case, a party). This is the way the LSAT has traditionally handled either/or statements, and thus why we teach it the way we do.

It's a lot like a rule that dictates "Either M or N must be in the fifth position."
In considering such a rule, no one questions whether or not the fifth position exists--it's just a question of who will take that spot. Similarly, in the case you considered, you should not question the existence of the party, but instead consider who will be in attendance.

I hope that's helpful--let me know.

Thanks!

~Steve