A?

@lerondagates, Let's start by diagramming the stimulus. To be capable of locomotion (A) an organism must be able to form representation (B) and to send messages (C). Locomotion is a sufficient condition, and representation & messages are necessary conditions. A- > B & C Such an organism must have a central nervous system (D). This premise presumes that for an organism to be able to form representation/ send messages, it must have a central nervous system. B&C -> D A-> D Thus an organism incapable of planned locomotion (A) does not have a central nervous system (D) ~A->~D This is a flawed argument, the only proper inference is that: ~D ->~A No nervous system -> no locomotion as nervous system is a necessary condition for locomotion. (A) correctly points out the flaw - the argument confuses a necessary condition, i.e. central nervous system for an organism possessing capacity, i.e . locomotion with a sufficient one. Since the conclusion given in the stimulus is no locomotion - > no nervous system, this conclusion is reached from the following premise: nervous system -> locomotion, where nervous system is a sufficient condition for locomotion. But there is no such premise in the argument, instead we have a premise saying locomotion -> nervous system, where nervous system is a necessary condition - hence the conclusion confuses the necessary for sufficient condition. Let me know if this makes sense and if you have any further questions.