Logical Reasoning

PT138 · S2 · Q25 If squirrels eat from a bird feeder

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If squirrels eat from a bird feeder, it will not attract many birds.

Conclusion (so)

If a bird feeder doesn't have protective cover, a bird feeder will not attract many birds.

Evidence

If a bird feeder has a protective cover, then squirrels won't eat from the feeder.

If squirrels eat from the feeder, it won't attract many birds.

Evaluate

Since this has three conditional logic claims (if / only if / if) and has ideas that show up multiple times (squirrels eat / attract birds / protective cover), we would probably be wise to diagram this symbolically.

And since we're doing Flaw / Parallel Flaw and we're seeing conditional logic, we can already be 90% sure that the flaw in the argument is an illegal negation or reversal (i.e. the Necessary vs. Sufficient flaw).

The author is trying to put together two conditionals to arrive at her conclusion. Since "squirrels eating" is the common term in the two conditional premises, it's supposed to be the middle link in the chain.

The author thinks she's combining these two premises:

No cover → Squirrels eat Squirrels eat → Not many birds

If those were actually the two premises, then she would correctly be deriving her conclusion:

No cover ---------------> Not many birds

The problem is the second premise says, Squirrels eat → No cover

The word "only if" is the opposite of "if". When we see "if", the idea that goes with that word ends up on the left side of the arrow (the sufficient condition). When we see "only if", the idea that goes with that ends up on the right side (sufficient condition).

Goal

The author is trying to make this sort of argument P1: A → B P2: B → C C: A -----> C

But one of the premises is reversed. So let's look for something like this:

P1: B → A P2: B → C C: A -----> C

In the original argument, both premises started with the same trigger "squirrels eat", just as in this algebraic recipe both premises start with the trigger B.

So we can have a couple things to look for quickly: - 2 premises, 1 conclusion, all conditional - the two conditional premises should have the same trigger

25.

The flawed pattern of reasoning in the argument above is most similar to that in which one of the following arguments?

  1. If a tire's pressure is

    Bad Premise Match

    It looks like all three claims are conditionals, but the two premises don't have the same trigger, so we know it's wrong. These are the two premise triggers: Pressure too low → Tire wears out prematurely →

    4% picked this

  2. Correct

    If a tire's pressure is

    Why this is right

    The two premises start with the same trigger: Pressure too low → wear out prematurely Pressure too low → neglects check And if we were to reverse that second premise, then we could derive the connection the author does in the conclusion: neglects → pressure → wear out check too low prematurely P1: B → A pressure too low → neglects check P2: B → C pressure too low → wear out prematurely C: A→ C neglects check → wear out prematurely

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

    80% picked this

  3. Tires wear out prematurely if

    Bad Premise / Conclusion Match

    The conclusion is not really presenting as a conditional. It's a prescriptive / normative idea. "We should make car owners aware of consequences". Yes, we could turn that into a conditional, like, "If car owner, then should be made aware", but we shouldn't have to contort the correct answer that much. If we didn't bail based on that, we would potentially be enticed by the fact that the two premise conditionals do have similar triggers. neglect check regularly → wear our prematurely neglect check regularly → unaware of fact We would now want a conclusion that tries to make a conditional relationship between those outcomes, something like this: "If tires wear out prematurely, then the car owner was unaware" or "If car own is unaware, then tires will wear out prematurely" The conclusion doesn't resemble either of those. The fact that it doesn't mention "wear out prematurely" tells us it can't be a match.

    3% picked this

  4. If a tire's pressure is

    Bad Premise Match Valid Logic

    It looks like all three claims are conditionals, but the two premises don't have the same trigger, so we know it's wrong. These are the two premise triggers: Pressure too low → Neglects to check → If we got sucked into thinking harder about this answer, we would discover that it's also valid logic.

    11% picked this

  5. If a tire's pressure is

    Bad Premise Match

    It looks like all three claims are conditionals, but the two premises don't have the same trigger, so we know it's wrong. These are the two premise triggers: Pressure too low → Driven on gravel roads →

    2% picked this

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