#help - I don't understand how we could know - without process of elimination - that B was the mistake the person was making. Why could we not say their line of reasoning is correct in that a defense attorney may be exploiting a known error in the testing system to make a generalization that the test should not be relied upon as a whole?

@RachelMeltsin I thought the same thing, but the explanation helped me understand it a bit more. The added example about the escape plan helped me see the need to ask what the point is really driving toward. In other words, what is the main point? I rephrase the text in question 5 to say "the status quo is not a sustainable, long-term solution, so they need to shut down." Doing this helped me see that the status quo not working in the long run isn't really the point, it's just emphasizing the need for the main point - to shut things down.

Finally, the reassurance that I don't need to understand all this perfectly gave me a little sigh of relief :)

One thing I don't quite understand: why do we not distinguish between the strength of assumptions based on how easy they would be to prove?

In this example, you could ask the owner if he has any other pets, making the assumption that "there wasn't another pet in the house that could have done this" provable. On the other hand, you can't really prove the assumption about Mr. Fat Cat's strength. Maybe he was very motivated and muscled the strength like the mothers do when they lift a car to rescue their baby. Maybe he wouldn't have the strength but managed to aim his body as a cannonball in just the right position, using the momentum?

In short, is there a spectrum of assumption reasonableness based on effort it would take to prove its truth?