Logical Reasoning

PT23 · S2 · Q19 Even in ancient times, specialized

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Even in ancient times, specialized farms (farms that grow a single type of crop or livestock) existed only where there were large commercial markets for farm products, and such markets presuppose urban populations.

Conclusion

The ruins in the site at Kadshim are probably from a mostly uninhabited ceremonial structure, not a densely populated city.

Evidence

The land in the region of Kadshim could never have supported any farms except mixed farms.

Specialized farms (the opposite of mixed farms) only occurred where there were large commercial markets, which only occurred within urban populations.

Evaluate

When we're doing a Flaw question and see conditional logic indicator words, then we immediately start to suspect that the author will mess up this conditional logic, usually doing the famous Necessary vs. Sufficient flaw.

What are the conditional logic indicator words we should be seeing in the first sentence? only where presuppose

only, only if, only where, only when = necessary indicators (put the attached idea on the right side of the arrow)

obnoxiously, "the only" is a sufficient indicator.

presupposes, implies, requires, depends on = necessary indicators (put the Required thing on the Right side of the arrow)

So the author said

Specialized → large commercial → urban farms markets populations

The author's conclusion is trying to establish that some ruins were from an .

Since the author is trying to prove "these ruins are not from an urban population", we have to understand how the author was attempting to use this logic chain in order to reach her conclusion of "not urban population".

The author is envisioning an illegal negation of this chain of logic:

Since we know ,

Specialized → urban farms populations

... the author is thinking, .

Specialized → urban farms populations

Goal

We need to either call out the formal conditional logic mistake, (Nec vs. Suff) or point out our possible objection --- it's possible that this region had mixed farms that catered to urban populations.

19.

Which one of the following is an error of reasoning in the argument?

  1. taking the fact that something

    Wrong Flaw: not Sampling

    The author's evidence doesn't provide a sample of a class of things. It provides a bunch of conditional ideas about what specialized farms required and about how specialized farms were impossible in the Kadshim region.

    9% picked this

  2. Correct

    taking the nonexistence of something

    Why this is right

    A necessary precondition of specialized farms is urban populations. Specialized farms require a large commercial market, and that only happens with an urban population. The author is pointing out that in the Kadshim region, there would have been a nonexistence of specialized farms. She then takes the nonexistence of specialized farms in the Kadshim region as evidence that urban population (a necessary precondition of specialized farms) wouldn't have been an option in this region. This is a fancy way of describing an illegal negation. Given A ? B, we can say that B is a necessary precondition for A. If an author reasoned, "Since Jerry isn't A, that must mean that Jerry isn't B", that would be an illegal negation. The author took the nonexistence of A as evidence that B was not true.

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

    69% picked this

  3. interpreting an ambiguous claim in

    Wrong Flaw: not Equivocation

    The author's argument isn't flawed because it used the same term or concept to mean two different things.

    3% picked this

  4. supposing that because two things

    Wrong Flaw

    Wrong Flaw: not Causal Bad Conclusion Match When an answer is structured like (assumes) that because X, Y then we can ask ourselves, "Does X match the Evidence? Does Y match the Conclusion?" Was the evidence here talking about two things that usually occur in conjunction with one another? We could stretch that. The author's evidence says that specialized farms usually (really: always) occur in conjunction with large commercial markets + urban populations. But then would the Conclusion match? Did the conclusion say that "specialized farms cause large commercial markets / urban populations"? No way.

    17% picked this

  5. drawing a conclusion that is

    Wrong Flaw: not Circular

    The conclusion is that "the ruins are probably the remains of an uninhabited ceremonial structure". There definitely was not a premise that said "the ruins are from an old ceremonial structure".

    1% picked this

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