Passage Summary: To move around with a plan, you need a brain and nervous system. Therefore, if you can't move around with a plan, you must not have a brain or nervous system.

Conclusion: Organisms that are unable to engage in planned movement do not possess a central nervous system.

Reasoning: Planned movement requires both an internal environmental map and the ability to signal muscles, both of which require a central nervous system.

Analysis: The theorist commits a classic 'Mistaken Negation' error. They establish that a central nervous system is a necessary condition for planned locomotion, but then incorrectly assume that the absence of locomotion implies the absence of the nervous system. You should look for an answer choice that describes this confusion between necessary and sufficient conditions. Just because you need a brain to drive a car doesn't mean everyone who isn't driving a car lacks a brain.