Logical Reasoning

PT118 · S4 · Q19 According to some astronomers, Earth

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According to some astronomers, Earth is struck by a meteorite large enough to cause an ice age on an average of once every 100 million years.

Conclusion (this warrants)

We should spend some money to determine whether there's a way to protect our planet from meteorite strikes.

Intermediate Conclusion (so)

We can expect Earth will be struck by an ice-age-causing meteorite in the near future.

Evidence

Earth gets hit by an ice-age-causing meteorite an average of once every 100 million years.

The last one came about 100 million years ago.

Evaluate

There are a couple complaints that come to mind. One is the sense in which the author is interpreting average / probability too literally.

If we know that , and the last five times we've rolled we haven't gotten a 3, it's not correct to say . It's still just a 1/6 probability.

if we say . That's interpreting average too literally.

Similarly, just because Earth has averaged one huge meteorite every 100 million years doesn't mean that we can expect the gaps between each meteorite to be literally 100 million years.

That's just an average. If it's 101 million years this time between meteorite strikes, then we're still 1 million years away from the next meteorite strike.

Thus, it wouldn't be true to say nor do we need to scramble into meteorite-defense planning. We have 1 million years to work on that, more than the entire species history of homo sapiens up to this point.

Goal

Find an answer complaining about interpreting average too literally, or failing to consider that if we're even slightly off from 100 million years, we're talking about a million year difference!

19.

The reasoning in the argument is most subject to criticism on the grounds that the argument

  1. makes a bold prescription on

    Not a Flaw

    There's nothing really unreasonable about making a bold prescription based on a high probability for a disastrous event. If there's a 70% chance of disaster, it's time to make some bold moves! The author's evidence did not establish a high probability of a disastrous event. We do not accept that we can expect Earth to be struck in the near future, because we're talking about an average occurrence of once every 100 million years, so the margin of error is over a million years!

    13% picked this

  2. presumes, without providing justification, that

    Opposite

    This saying that the author avoided committing the famous Gambler's Fallacy -- instead of thinking "since none of the last five rolls were a 3, the next roll of the die will probably be a 3", this answer says our author was thinking, "Hogwash! The previous events don't influence the probability of what's coming." Our author is thinking that "the fact that we haven't had any big ol' meteorites in the last, nearly 100 million years indicates that we can expect such a meteorite in the near future".

    11% picked this

  3. Correct

    moves from evidence about the

    Why this is right

    This is just making the complaint that the author is treating average too literally. If I know that there's a Presidential scandal, on average, once every 18 months, I can't use that to make specific predictions about when the next scandal will be. It's just an average. Sometimes the gaps between will be shorter than 18 months, sometimes longer. Similarly, sometimes it might be 80 million years between strikes, sometimes 120 million years between.

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

    69% picked this

  4. fails to specify the likelihood

    Not an Objection

    Since the pronoun in "such meteorite strikes" and "such a meteorite" refers back to "a meteorite large enough to cause an ice age", it's already baked into the concept of what we're talking about that the meteorite would cause an Ice Age. That's not our problem with the reasoning.

    3% picked this

  5. presumes, without providing justification, that

    Contradicted

    The author's conclusion is just saying, "let's spend some money to determine whether there is or isn't some feasible means". She's not assuming the answer will be YES, just assuming it's worth trying. We could fix this by saying, "presumes that the chance of there being a feasible means is high enough that it warrants funding".

    4% picked this

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