Q10 - A distemper virus has caused

[willaminic]

Can anyone explain why E is wrong? Thank you.

[bbirdwell]

Look at the argument core.

Conclusion:
the pollution weakened the immune systems

Premise:
the virus killing them is normally latent

Now, consider what gaps there are in this logic. What MUST be true in order to draw the conclusion above?

It's a causal argument, so the first thing to consider is alternative causes. If we are to conclude that the pollution is causing the seals to die (via the virus), then we must assume that nothing else out there is killing the seals, that something in their diet didn't weaken their immune systems, that a big asteroid didn't kill them... whatever.

(A) nope! We do not need to assume this in order to draw the conclusion above.

(B) appealing, but no. doesn't matter when the pollution got there.

(C) yes! Notice how if a virus mutation DID happen, the conclusion is weakened -- now there's another candidate for the cause (the virus), and there is less certainty that the pollution was the cause.

(D) nope! doesn't matter what the pollution is like in other places.

(E) close! I see why this is appealing, however it's not as strong as (C). For one thing, "some species" is too vague. What if the species in question comprise only 1% of the seals' diet? Not such a big deal, then. If this choice said something more like "the seals' PRIMARY or ONLY source of food is going extinct..." then it would be better.

[WaltGrace1983]

I'd also like to add some more analysis on (E) and how I looked at it.

So the argument is a very strong one (very good for handling Assumption questions!). The premise is saying, "these seals are dying there must be a reason!" The conclusion is saying "clearly it must be the pollution!" So how do we handle this? We have to get rid of all competing explanations by assuming that all competing explanations didn't happen as Brian pointed out above.

The reason why (E) is wrong is because it actually goes against the conclusion by providing the existence of a competing explanation - the exact opposite of our task! (E) is saying "well maybe it could be because the species that provide food are dying." So what if they are dying because of the pollution perhaps (E) is implying that it is the loss of food that is contributing to the seals' death!

Hope that helps someone!