LSAT 131 | Section 3 | Logical Reasoning: Q19

LR Question 19 Explanation

QUESTION TEXT: If understanding a word always involves knowing its

QUESTION TYPE: Must be True

FACTS: IF [Understanding → knowing dictionary definition] → THEN [Understanding → knowing the words in the dictionary definition]

Some people don’t know the dictionary definitions of the words they say.

ANALYSIS: This is one of the stranger stimuluses I’ve seen. The conditional statement is actually an embedded conditional statement. It’s saying “If this conditional statement is true, then this other conditional statement is true”. Which isn’t a common format on the LSAT.

Despite that, this is fairly easy to understand. You don’t need to know the full logic of the conditional to know that it’s basically saying “understanding → dictionary definition”. The claim about babies seems to be opposition to this. The people who don’t know dictionary definitions are saying words: do they understand them? If they do, the conditional can’t be true.

Honestly, this is structurally about the most convoluted conditional statement question I’ve ever seen. I’ve never seen another with similar structure. And yet, if you don’t bother drawing this, I think it’s actually easier to think about this question intuitively.

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1. We don’t know this. The conditional didn’t say “if you understand, you know the dictionary definition.” Instead, the conditional statement gave a conditional statement as the sufficient condition. Makes the head spin, don’t it?
   It’s like saying “If unicorns are real, then I am a billionaire.”
   It turns out unicorns aren’t real, so the sufficient condition (which is itself a conditional, “U → R”) doesn’t trigger, and sadly I am not a billionaire.
2. We have no evidence about who can understand. The stimulus actually gave us no statement that said “If X → understand”. We have no sufficient condition for understanding a word.
3. This doesn’t follow. It’s possible that some words can be understood without understanding their definitions, but that babies also can’t understand words. (They’re babies, c’mon)
4. This is insane. The first part means “you can understand some words by reading around for context”. The second part means “You can understand a word in total isolation from the rest of the language.”
5. CORRECT. This answer is yet another conditional. IF babies understand words, then that means understanding is possible without understanding all dictionary definitions. Which shows the first part of the condition is not true: It is not the case that understanding a word always involves knowing its dictionary definition.