Logical Reasoning

PT143 · S3 · Q16 Theorist: To be capable of planned

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Theorist: To be capable of planned locomotion, an organism must be able both to form an internal representation of its environment and to send messages to its muscles to control movements.

Conclusion (Thus)

An organism incapable of planned locomotion does not have a central nervous system.

Evidence

An organism capable of planned locomotion must be able to form an internal representation of its environment and to send messages to muscles, both of which requires a central nervous system.

Evaluate

Whenever we're doing Flaw and we come across Conditional Logic, we immediately start suspecting that the argument will commit the #1 famous flaw, Necessary vs. Sufficient, in which the author presents some conditional logic premise that he then applies in an illegal reversed or negated fashion.

Both premises stated requirements, using the necessary indicator "must".

We read conditionals like A → B two main ways: 1. if A, then B 2. A requires B

There are other ways too ("all A's are B" / "A implies B"), but these two are the most common and useful.

So if we're reading that , it would look like this:

Planned → internal rep locomotion + msg-sending

When the 2nd sentence adds on another requirement, we can keep the chain going.

Planned → internal rep → central locomotion + msg-sending nerv sys.

The two premises combine to show us that "Planned locomotion requires a central nervous system".

capable of planned → central locomotion nerv sys.

The conclusion is an illegal negation of this:

incapable of planned → no central locomotion nerv sys.

Goal

Look for an answer calling out the illegal negation, which LSAT describes as confusing a Necessary and a Sufficient condition.

Or look for an answer pointing out the possibility that an organism could have a central nervous system and still be incapable of planned locomotion (a central nervous system is required for locomotion but it doesn't guarantee an organism would have it.)

16.

The theorist's argument is flawed in that it

  1. Correct

    confuses a necessary condition for

    Why this is right

    We learned that a central nervous system is necessary for an organism to possess the capacity of planned locomotion. But the author is acting like a central nervous system guarantees the capacity for planned locomotion. That would look like this: central nerv sys ? planned locomotion no planned locomotion ? no central nerv sys This conditional matches the author's conclusion, but it's a backwards or negated version of the conditional relationship provided in the evidence.

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

    87% picked this

  2. takes for granted that organisms

    Not Assumed

    Since this answer begins with takes for granted / presumes, we can ask ourselves whether this qualifies as a Necessary Assumption. Did the author make this reasoning move: "If an organism can send messages from its central nervous system to its muscles, then it must be capable of locomotion"? No, the author never tried to prove that anything was capable of locomotion. The author's conclusion is trying to prove something about organisms that are incapable of locomotion.

    6% picked this

  3. presumes, without providing justification, that

    Not Assumed / Too Strong: only

    Since this answer begins with takes for granted / presumes, we can ask ourselves whether this qualifies as a Necessary Assumption. Did the author need to assume that "the only purpose of having an internal representation of one's environment is for planned locomotion"? Of course not, that's way too extreme. The only purpose mentioned was planned locomotion, but that doesn't mean the author assumes that locomotion is the only purpose. When someone says "Black lives matter", the only lives mentioned are black lives, but that doesn't mean the speaker believes that black lives are the only ones that matter.

    3% picked this

  4. takes for granted that adaptations

    Not Assumed

    Since this answer begins with takes for granted / presumes, we can ask ourselves whether this qualifies as a Necessary Assumption. Did the author assume a biologically useful purpose (i.e planned locomotion?) originally came about for that purpose? No, the author isn't saying anything about the evolutionary history of a certain biological feature. The author is discussing biological requirements of a certain feature, but there's nothing in this conversation about adaptations or what "purpose" an adaptation had in the first place. (Truthfully, using the term "purpose" in relation to evolution is a misnomer always. Evolution isn't planning to be useful. It's a bunch of random mutations, and the ones that turn out to be useful or have a beneficial purpose start showing up more and more in the gene pool until they become a trait of the species itself.)

    2% picked this

  5. presumes, without providing justification, that

    Not Assumed

    Since this answer begins with takes for granted / presumes, we can ask ourselves whether this qualifies as a Necessary Assumption. Did the author assume that an organism with a rudimentary nervous system can form an internal representation of its environment? No. We never talked about different levels of complexity with nervous systems. We have no idea what the author believes about rudimentary vs. more complex nervous systems.

    1% picked this

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