Logical Reasoning

PT147 · S1 · Q4 If a civilization as technologically

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If a civilization as technologically advanced as human civilization existed on another planet and that planet were within 50 light years of Earth, that civilization would have found evidence of intelligent life on Earth and could have easily contacted us.

Conclusion (thus)

Scientists can rule out the possibility of finding a civilization as technologically advanced as us that's within 50 light years of distance.

rephrase: We will not find alien life as sophisticated as us that's within 50 light years.

Evidence

If such life existed (as advanced as us + within 50 light years), that civilization would have already found evidence of us and could have easily contacted us.

Evaluate

The author is trying to make an argument by contrapositive. She's refuting a claim by showing that one of its implications doesn't hold.

If X were really true, then Y would be true. Since Y isn't true, we can rule out the possibility of X being true.

In this argument, that felt like this:

If there were really close/smart aliens, then they would have found evidence of us and could easily contact us.

Since (they haven't found evidence of us / they can't easily contact us) we can rule out the possibility that there are close/smart aliens.

Thus, the author is missing, or assuming, that second premise, where you factually trigger the contrapositive.

If I just say, , then I"m assuming that "Y is not trueIf there were really aliens out there, they would be able to contact us, so we would have heard from them by now."

If we accept that "earthlings have not been contacted by aliens yet", does that really prove that there aren't aliens out there with the technology/proximity to contact us?

No, we could always argue that there are aliens who are advanced enough and close enough to notice us and be aware of us, but they might choose not to contact us. After all, if they look around at the current state of humanity, they would see a lot of combative imperialism and an inability to take care of the local ecology. Who wants a new friend like that?

Goal

Look for something like .

4.

Which one of the following is an assumption required by the argument?

  1. Scientists who are searching for

    Too Strong: generally

    It doesn't matter to this author whether scientists who search for alien life spend 51% of their time looking for technologically advanced life forms and 49% of their time looking for simpler forms of life, or vice versa. So the author doesn't need to assume anything about what scientists generally do. The word/concept of "most" is wrong on Necessary Assumption 99% of the time. It's only needed when the conclusion is using the concept of most. This conclusion is talking about whether something is possible.

    1% picked this

  2. There is no reason to

    Illegal Negation / Fake Opposite

    One of the top 3 wrong answer patterns on Necessary Assumption is this idea of a Fake Opposite. We usually use "illegal negation" to mean taking a conditional like, "If in NY, then in USA" and flipping the lightswitch on the truth values to illegally arrive at the notion that, "If not in NY, then not in USA". A Fake Opposite is basically doing the same "flipping the lightswitch" inversion, but it's doing it to a claim that felt more like a fact and less like a conditional rule. If we're told that, "Jim bought a lot of food when he went shopping with his sister", then a Fake Opposite trap answer would say, "Jim doesn't buy a lot of food when he isn't shopping with his sister (or, 'when he shops by himself', or 'when he shops with his brother')". The conclusion said, "There's no hope of finding smart aliens closer than 50 light years", so this Fake Opposite is giving us, "There is utmost confidence of finding smart aliens farther than 50 light years".

    1% picked this

  3. If scientists received a message

    Too Strong: decipher fully / all messages

    There's no reason to think this author believes that we humans would be able to decipher every single part of every single message we would receive from a technologically advanced alien civilization. What a crazy idea for anyone to say. The author hasn't affiliated herself with this indefensible notion.

    4% picked this

  4. Correct

    A technologically advanced civilization on

    Why this is right

    The author is assuming that, "If there were really smart aliens nearby, they could contact us (and would have already. They haven't contacted us yet.) Thus, there aren't smart aliens nearby." That part about thinking, "if they could contact us, they would have already" is what this answer is getting at. The author assumes that a smart alien that found evidence of us and who had the means to contact us would contact us. If we negate this and tell him that smart aliens would not want to contact us, it hurts his argument. It allows us to say that, "the fact that smart/nearby aliens haven't contacted us doesn't mean they don't exist; it could just mean that they have observed us but don't have any desire to contact us."

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

    91% picked this

  5. Intelligent life forms on other

    Too Strong: all signs

    There's no reason to think this author believes that aliens would understand every single possible sign of intelligent life. They might see people flying kites they've built, and have no idea that this is a sign of intelligent life. It might just look like a winged creature hovering in mid-air. If we negated this and said, "Hey, author, aliens would only be able to interpret about 99% of what we do as signs of intelligent life", that wouldn't hurt the argument at all.

    3% picked this

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