QUESTION TEXT: Anatomical bilateral symmetry is a common trait….
QUESTION TYPE: Parallel Reasoning
CONCLUSION: Bilateral symmetry must help organisms survive.
REASONING: It is common. Anything that is common must help organisms to survive.
ANALYSIS: This is a good argument. We’re given one sufficient necessary statement:
No advantages ➞ no common
We can take the contrapositive, and we get:
common ➞ helps organism to survive
So since bilateral symmetry is common, it helps organisms to survive.
The structure is: taking the contrapositive of a premise, and combining it with a known fact.
___________
- There might be some other reason Sawyer was appointed. Maybe the city wants the negotiations to fail, and only Sawyer can be counted on to ruin things effectively.
- This is a bad argument. It’s practically circular: its only evidence is that people think highly of Turnbull. But opinion can never prove a statement of fact.
- CORRECT. The premise we’re given is this:
No superior skills ➞ Not appointed
Since Powell was appointed, she must have superior skills. This is the contrapositive combined with a known fact.
- This isn’t a good argument. Rivers never negotiates unless Varga isn’t there. But that doesn’t mean rivers always negotiates when Varga isn’t there.
- This is a good argument. It’s reasonable to expect Wong to be appointed, though it isn’t certain. But this doesn’t have the same contrapositive structure as the original argument.
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