Logical Reasoning

PT23 · S3 · Q19 When a stone is trimmed by a mason

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When a stone is trimmed by a mason and exposed to the elements, a coating of clay and other minerals, called rock varnish, gradually accumulates on the freshly trimmed surface.

Conclusion (it follows that)

The monument was built long before the arrival of Europeans in the Americas in 1492.

Evidence (Since)

On the monument, the organic matter trapped beneath the varnish on stones was over 1,000 years old.

When a stone is trimmed, rock varnish gradually accumulates on the trimmed surface, and the organic matter must have started growing shortly after it was trimmed.

Evaluate

This argument is tricky to understand at first. Essentially, though, it's saying that when you trim a stone, then organic matter starts to grow on its surface. Since the organic matter on the stones in this monument is over 1,000 years old, then presumably the stone was trimmed over 1,000 years ago.

Since we're in the 2020's, this is saying that this stone was trimmed around the year 1000, if not before that. Thus, this monument long predates the arrival of Europeans in 1492.

There's no reason to specifically be bringing up Europeans; it's just an iconic date people know, ().

Okay, so there seem to be two different spots where we could try to resist the reasoning moves the author is making:

Given that ... the organic matter on the stone is over 1,000 years old, could we still say ... the stone was trimmed less than 1,000 years go?

If the stone was trimmed only 500 years ago, and then rock varnish started to accumulate on the freshly trimmed surface, is it possible that some organic material from 1,000 years ago got underneath varnish? Yes, there are some possible ways we could make that work. What about the second reasoning move; can we fight that one?

Given that ... the stone was trimmed more than 1,000 years ago, could we still say ... the monument was built after 1492?

Potentially. Maybe there were some super old trimmed stones (from pre-1000) laying around and they decided to build a monument with them in the year 1500.

Someone might decorate the path to their front door with stones that are 100 years old, but that doesn't mean that the decorative walkway itself is 100 years old.

Goal

Find an answer that can help us argue that or one that can help us argue that .

19.

Which one of the following, if true, most seriously weakens the argument?

  1. Rock varnish itself contains some

    No Impact

    The author wasn't assuming that rock varnish was purely inorganic matter, so this answer can't hurt her argument. The organic matter that was dated at 1,000 years lies beneath the varnish, not within it, so this answer isn't offering some alternate explanation for the organic matter.

    13% picked this

  2. Correct

    The reuse of ancient trimmed

    Why this is right

    This allows us to argue that "even though the stones used in the monument are over 1,000 years old, the monument itself isn't over 1,000 years old. It may have been built after 1492." After all, it was a common practice to reuse ancient trimmed stones. So, the Andean people might have built this monument in 1600 A.D., using stones that were originally trimmed in 900 A.D.

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

    69% picked this

  3. The Andean monument bears a

    No Impact

    Comparing how this monument looks visually to monuments in Western Asia doesn't tell us anything about when this monument was built. If anything, the fact that this monument has similarities to monuments in ancient Asia would make this monument seem like it might be old, which would just strengthen the author's conclusion.

    1% picked this

  4. The earliest written reference to

    No Impact

    Knowing when writers first wrote about the monument does not provide any clue as to when this monument was built. It's possible that when the monument was built that written language didn't even exist for the culture that made it. So we would never base our estimation of age on when someone first wrote about something.

    6% picked this

  5. Rock varnish forms very slowly,

    No Impact

    This answer provides a potential causal mechanism by which one could delay the onset of rock varnish. If that were the case with the stones in this monument, it would mean that stones were even older than the author already thinks they are. Once the varnish started accumulating, it trapped whatever organic particles were on the rock's surface, and since there is organic material that's over 1,000 years old trapped under the varnish, we know the varnish started accumulating over 1,000 years ago.

    11% picked this

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