LSAT 75, Logical Reasoning II, Q16, LSATHacks

LR Question 16 Explanation, by LSATHacks

QUESTION TEXT: Theorist: To be capable of planned locomotion…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: No planned locomotion ➞ no central nervous system

REASONING: No central nervous system ➞ no planned locomotion

ANALYSIS: This argument makes a classic flaw: incorrect reversal. That’s when you reverse the conditions of an if/then statement. I.e. Taking “all cats have tails” to mean “This dog has a tail so it must be a cat”.

Note that the first sentence of the stimulus is just context for why central nervous systems are needed for locomotion. It’s not structurally relevant to the argument.

Note on B, C and E: Scientific questions often have nonsense answers. They take two terms from the argument, and reverse them or combine them in a new way. An answer can’t be a flaw if the author didn’t say it.

They’re simply gibberish intended to bog you down. This is why it’s important to prephrase answers. If you knew this argument made an incorrect reversal, you could quickly skip over these gibberish answers.

___________

1. CORRECT. See the analysis above.
2. The argument didn’t say this! This answer incorrectly reverses what the author said in the first sentence.
3. The author never mentioned biologically useful purposes.
4. This is a different flaw.
   Example of flaw: Our hands let us use computers, so hands must have evolved so that we can use computers.
5. The author didn’t say this! This answer says that nervous systems lead to the ability to form internal representations (Nervous system ➞ representation).
   But actually, the author said that nervous systems are a necessary condition for forming an internal representation (representation ➞ nervous system)