Scientist: Given the human tendency to explore and colonize new areas, some people believe that the galaxy will event...

Kyle on May 12, 2020

difference between choices A and D?

I was between the two and ended up picking A. I just couldn't find a way to rule either out. It seems like they almost state the same thing. Could someone explain this please?


Shunhe on May 13, 2020

Hi @kyleprzy10,

Thanks for the question! So let’s take a look at the argument real quick. We’re told that humans like to colonize, and so some people think that the galaxy will be colonized, and if that were the case, then most humans alive would be alive then (since there would be trillions of humans then). The author then notes that we are representative humans, and so from an objective point of view, there’s a high probability we’re alive during this time. The author then concludes that since we’re not alive during that period, the chances that colonization of other galaxies actually happens is low.

Now we’re asked to evaluate how the argument proceeds. Let’s take a look at (A), which tells us that the scientist reasons that because an event hasn’t occurred, the event has a low probability of not occurring. In this case, “the event” would refer to colonizing other galaxies. But that’s not what the argument does. If that were the case, the argument would read something like “since we haven’t colonized the galaxy, it’s unlikely that we’ll colonize the galaxy.” But the argument is actually based on the probability of us being alive during a time when colonization hasn’t happened, which is different.

(D), on the other hand, accurately sums up what the argument does. The argument infers that since an event that is taken to be likely on a given hypothesis has not occurred (the event here being colonization, and the hypothesis being that the galaxy would eventually be colonized), the hypothesis (of colonization) is probably false.

Hope this helps! Feel free to ask any other questions that you might have.