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June 2007, Logical Reasoning 1, Question 5


Question five. Starting with a question stem, we see the phrase count as evidence against. So this is a weaken question. Our job on a weaken question is to attack the argument's assumptions. But in order to find the assumptions, we need to know the conclusion and the evidence of the argument.

This argument is a causal argument trying to establish that the warming that's happened over the last century is the result of the buildup of minor gases in the atmosphere. The evidence for this takes two forms. The first is just the setup that establishes that there has been warming over the last century, and the last bit of information that tells us how they think that the gases are responsible for the warming.

The gases are blocking the outward flow of heat from the planet. There are two major assumptions here. They are assumptions that we see on pretty much every causal argument. That is, every argument where you're trying to prove that something caused something else, requires the assumption that first, nothing else caused that thing that you're saying got caused, so nothing else caused the warming.

And it also requires believing that there is nothing physically or temporarily standing in the way of the thing that you are saying is the cause, bringing about the effect. So here, there is nothing standing in the way of the gases causing the warming. So we're gonna go to the answer choices looking for something that will attack one of those assumptions.

Answer choice A gives us some information about some of the gases. Some of the gases were produced by industrial pollution, and only some of them. The source of those gases isn't really relevant to the question of whether those gases caused the warming or not. So go to answer choice B.

Now answer choice B would be a problem for our second assumption. If most of the warming occurred before 1940 and most of the buildup of minor gases occurred after 1940, well, then it's very unlikely that the gases caused the warming. Essentially, there is something standing in the way of the gases causing the warming.

The timing is standing in the way. So answer choice B attacks an assumption. It weakens the argument. It is our answer. Let's glance at the other answers just to see what's wrong with them. Answer choice C would be great if they established that the solar radiation had been substantially higher over the last century, if there was a lot more solar radiation that could explain where the warming was coming from.

But this answer just says that over the last century, certain years had more solar radiation than others. Answer choice D, well, it tells us that there are some particles that come from volcanoes and other places that can reflect the sun's radiation back into space, which would really counteract the warming. It wouldn't help us explain where the warming came from.

So D is not our answer. And E, it tells us that the accumulation of minor gases has been greater over the last century than any other time in Earth's history, which would actually strengthen the argument. It would provide some evidence that it is the gases because hey, they weren't around before the warming started.

They coincided with it. So answer choice B is our answer.

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