Logical Reasoning

PT157 · S2 · Q20 The olecranon process is a bony

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The olecranon process is a bony part of the mammalian elbow.

Conclusion (hence)

Megatherium was probably a predator.

Evidence

Predatory mammals generally have short olecranon processes.

Megatherium had a short olecranon process.

Typically, the shorter the olecranon process, the faster the forelimbs can move, and predators need to move their forelimbs very quickly.

Evaluate

If we tried to argue the anti-conclusion, "Meg wasn't a predator", the author would be like,

One way to respond could be to say, "Prey animals also tend to have short OP's." The evidence never ruled out that possibility.

We could also try to argue that Meg has a short OP for a different reason. Sure, predators need short OP's so that their forelimbs can move quickly when attacking prey. But maybe there are some herbivores who need quick moving forelimbs to pick the leaves off a tree. Perhaps Meg is an example of a non-predator species that needed quick forelimbs for some other reason.

The form of this argument is an illegal Most reversal.

In conditional logic we know this difference: VALID INVALID P: if X, then Y P: if X, then Y P: Meg is X. P: Meg is Y. C: so, Meg is Y. C: so, Meg is X.

The same thing applies with Most statements. VALID INVALID P: most X's are Y P: most X's are Y P: Meg is X. P: Meg is Y. C: Meg is probably Y. C: Meg is prob X.

This argument did that invalid Most reversal. P: Most predators have short OP. P: Meg has short OP. C: Meg is probably a predator

Goal

The correct answer might call out this illegal most reversal or it might give us some way to argue that Meg was a non-predator.

20.

The argument is most vulnerable to criticism on which one of the following grounds?

  1. Correct

    It fails to address the

    Why this is right

    When we see an answer begin with fails to consider / ignores possibility, we ask ourselves "would it weaken"? If we said, "Hey, author -- most mammals with short OP's are not predators", would that weaken? Hell yeah! Why does the author think that Meg is probably a predator? Because Meg has a short OP (and most predators have short OP's). We can say, "Sure, Meg was a mammal with a short OP, but most mammals with short OP's are not-predators. Thus, it's likely that Meg was not a predator." Boom! This answer is getting at the illegal Most reversal. To make a valid argument, the author would have needed to say, P1: Most mammals w/ short OP's were predators P2: Meg was a mammal w/ a short OP. C: Thus, Meg was probably a predator. The argument didn't give us that correct 1st premise. It gave us, "Most mammals that were predators had short OP's." This answer choice is pointing out the flaw by denying the correct premise. It's saying, "Most mammals w/ short OP's were not predators".

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

    60% picked this

  2. It takes for granted that

    Bad Assumption

    The only reason mentioned for why predators need to move their forelimbs quickly is to attack prey, but that doesn't mean the author needed to assume that there are no other reasons for predators to move their forelimbs quickly. If we negated this claim and said, "Hey author, predators ALSO need to move their forelimbs quickly for the sake of attracting a mate", that wouldn't hurt the argument at all. That wouldn't create a way for us to argue that Meg was not a predator.

    25% picked this

  3. It overlooks the possibility that

    Irrelevant

    Would it weaken the argument at all if we said, "Hey author -- Meg could have been a successful predator even if it didn't have a short OP"? No. The author was never claiming that Meg needed a short OP in order to be a successful predator. The author only claimed that Meg had a short OP and thus probably was a predator.

    5% picked this

  4. It takes for granted that,

    Irrelevant Comparison

    In order to conclude that Meg was a predator, did the author need to assume anything about how the average OP of extinct mammals (predatory and non-predatory) was no shorter than the average OP's of living mammals? Definitely not. The author is only trying to classify whether Meg was / wasn't a predator. That argument doesn't rely on any comparison between the entire class of extinct mammals to the entire class of existing mammals.

    6% picked this

  5. It fails to address the

    Out of Scope

    Would it weaken the argument at all if we said, "Hey author -- a long OP might have some advantages!" Of course not. The author was never saying that a long OP was worthless trash with no benefits. This argument wasn't designed to prove that shorter OP's are superior and that longer OP's are useless.

    5% picked this

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