Logical Reasoning

PT154 · S1 · Q25 Each major earthquake

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Each major earthquake in this region has been preceded by a series of minor tremors.

Premise 1 (before/after correlation)

Each major earthquake has been preceded by minor tremors. Each X has been preceded by Y.

Premise 2 (fact)

The region has been experiencing minor tremors. Y has been happening.

Conclusion (certain prediction)

An earthquake's a 'comin. X will happen

Evaluate

It wouldn't be unreasonable to conclude something like, "So there might be an earthquake coming", but we can't conclude so certainly that an major quake will come.

We know that every quake has been preceded by tremors, but it's possible that many times there have been tremors that weren't followed by an earthquake.

We could understand this flaw as a Necessary vs. Sufficient error, if we think of that first premise as a conditional.

Each is a sufficient indicator (left side idea), so we'd have: Major quake → preceded by tremors

The argument is thinking, "if tremors, then major earthquake."

Goal

Look for something that feels like an illegal backwards move, either with conditional logic, or with a before/after.

25.

Which one of the following arguments exhibits a pattern of questionable reasoning most similar to that exhibited by the argument above?

  1. In the past, a major

    Trap

    Bad Premise Match Topic Match: natural disasters The first sentence doesn't seem to work as a match, because it's actually causal, "Hurricane resulted from Tropical Storm". In the original argument, the relationship was just temporal, "Each quake was preceded by tremors". Even if we forgave that, a matching structure would go on to say "Since we have seen tropical storms, there will be a hurricane".

    5% picked this

  2. This river has overflowed in

    Weak Premise Match

    This is almost right, but this argument says: every time we've had x, y came after. x is happening. Thus y will happen. The original argument said: every time we've had x, y came before y is happening. Thus x will happen Original Argument This Answer before each quake after each snowy came tremors winter came flood the before (tremors) the before (snowy is happening winter) is happening ----------------------- ----------------------- the after (quake) the after (flood) will happen will happen

    28% picked this

  3. On planets other than Earth,

    Bad Premise Match

    There's no "every time X happened, Y came prior" premise to get us started. And the conclusion isn't making a certain prediction "it's stating a presumed similarity about the past". Let's bail.

    3% picked this

  4. The introduction of non-native species

    Bad Premise Match / Valid Logic

    I'm not getting past the first sentence of this one. It's causal again, like (A). introducing x always results in y If we do end up reading the whole thing, we also find out that it's a logically valid argument.

    7% picked this

  5. Correct

    So far, all local outbreaks

    Why this is right

    This, just like the original argument, says: every time we've had x, y came before y is happening. Thus x will happen Original Argument This Answer before each quake before each outbreak came tremors came high infection the before (tremors) the before (high is happening infection) is happening ----------------------- ----------------------- the after (quake) the after (outbreak) will happen will happen

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

    56% picked this

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