Logical reasoning PrepTest 133 · Section 2 · Question 6

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Paleontologists - Birds descended from dinosaurs
New evidence - Bird fossils that are 20m years older than the dinosaurs they supposedly descended from
Conclusion - Birds aren't descended from dinosaurs

Answer Anticipation:
When you're tackling an Errors in Reasoning question, you should be looking for elements that lend themselves to being flawed. Here, there's a huge one—that conclusion has extremely strong language. Not a single bird descended from not a single dinosaur.

When the conclusion is that strong, the premises better be pretty strong in order to support it. Do we have equally strong premises here?

Not at all. One set of fossils were found that predate the dinosaurs that scientists believe were the progenitors of the birds. First off, one example doesn't allow the conclusion of such a strong generalization. Second, the theory sets out what paleontologists generally claim, not what is true—they could be wrong and there could be a much older birdlike dinosaur species.

The premises here are not nearly strong enough to support the absolute generalization in the conclusion.

Answer Explanation:
This answer reflects the flaw in the argument. It goes from one example that contradicts what paleontologists believe to a conclusion that states the paleontologists are completely wrong. That's too much of a jump.

Key Takeaway:
The strength of the conclusion needs to be met or exceeded by the premises supporting it for it to have a chance at being valid. Very strong conclusions need very strong premises. When an argument has as strong a conclusion as this one, you should check to see if the premises are sufficiently strong.

Incorrect. Counterevidence is provided—those bird fossils that are older than the supposed dinosaur bird progenitor do contradict the belief of the paleontologists.

Incorrect. There's no personal attack and the argument presents evidence that counters their theory, so this attacking the person flaw answer is wrong.

Incorrect. This possibility would align with the conclusion that birds didn't descend from dinosaurs, so it's not something the argument fails to consider.

Incorrect. This answer aligns with the argument—if birds and dinosaurs both descended from a third type of animal, then birds didn't descend from dinosaurs, as the conclusion states. As such, the argument doesn't ignore this possibility.