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General questions relating to LSAT Logical Reasoning.
  • Posts: 5
  • Joined: Nov 02, 2020
I came across this statement from PT39 S2 Q18. Wondering if I can get help with diagramming it:

No one without a deep desire to communicate can be a blues musician.

I translated it to "If you are a blues musician, you have a deep desire to communicate." I diagrammed it as

Blues Musician :arrow: Deep Desire to Communicate

Am I correct, or completely out to lunch? Thanks!
 Robert Carroll
PowerScore Staff
  • PowerScore Staff
  • Posts: 722
  • Joined: Dec 06, 2013

Looks like you're skipping lunch! What you said looks perfect to me.

I think there are two ways to get to your result:

First way: Use the Unless Equation. "Without" is one of the four words (unless, except, until, without) that trigger the Unless Equation. To employ that equation, we follow these steps:

Step 1: Whatever "without" modifies is the necessary condition. So "a deep desire to communicate" is necessary.

Step 2: Negate the other part of the statement. That negation becomes the sufficient condition. The other part here is "No one...can be a blues musician." This is already negative. When we negate it, the double negations cancel, so we get, as a sufficient, "can be a blues musician."

That's your diagram.

Second way: Exploit the fact that the statement is structured as a "No thing with quality X has quality Y" conditional statement. "No thing with quality X has quality Y" is equivalent to "Anything with quality X lacks quality Y," or "If X then not-Y." So we get: "If you don't have a deep desire to communicate, you can't be a blues musician." You can keep that or contrapose it - the contrapositive says "If you are to be a blues musician, you must have a deep desire to communicate," which again gets diagrammed like what you said.

Robert Carroll

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