Logical reasoning PrepTest 158 · Section 4 · Question 6

When we see "fails to consider" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Would this weaken the author's argument if true?"

This answer choice wouldn't weaken the argument's conclusion. The argument's conclusion doesn't consider "other types of pollution not involving ozone." Notice that the conclusion only applies to "ozone-related health costs." So, it doesn't matter if other types of pollution increase health costs. That wouldn't change whether the air pollution measures reduce the "ozone-related health costs."

Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Passage Summary:
Air pollution measures would reduce ozone levels in the city by one-fifth. The ozone levels cause $5 billion in health costs. So, the air pollution measures would reduce ozone-related health costs by $1 billion.

Strategy Overview:

1. Argument or facts? Always argument, so identify premises and conclusions of argument
2. Anticipate why the premises are not enough to prove that the conclusion is true. 
1. Checking to see if a common logical fallacy is committed is very helpful.
3. Use anticipations to select the answer choice that:
4. Accurately describes the reason why the premises are not enough to prove that the conclusion is true

Answer Anticipation:
On an Errors in Reasoning question, we should take the time to articulate why the premise or premises aren't enough to prove that the conclusion is true. To help organize our thought process, we can think about the common flaws that arguments commit over and over again.

Experienced LSATers will immediately notice that the conclusion brings up a new concept that wasn't discussed in the premises. The conclusion brings up reducing ozone-related health costs out of (excuse the pun) thin air. The premises never discuss how to reduce these costs. They only discuss how much the air pollution measures will reduce ozone levels and the costs imposed by current ozone levels. When we see a new idea pop up in a conclusion, there's a good chance the argument commits a concept switch (also known as an equivocation flaw). That means the author thinks a concept discussed in the premises is roughly the same as a different concept the author brings up in the conclusion.

With this concept switch in mind, we can ask ourselves how the author determined that we can save $1 billion dollars if we implement the air pollution measures. Which premise is at least somewhat similar to that idea? Well, the first premise tells us that air pollution measures would reduce ozone levels in the city by one-fifth. Since the current cost of ozone levels is $5 billion, a one-fifth reduction in costs would save $1 billion. There's the concept switch — the author assumes that because the air pollution measures will reduce ozone levels by one-fifth, the measures will also reduce ozone costs by one-fifth. That's not necessarily true — reducing ozone levels may have no effect on the costs imposed by ozone levels! The correct answer will almost certainly describe this flaw.

Answer Choice Explanation:
When we see "presumes, without providing justification" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Does the author believe this, and would this strengthen the argument?"

In this case, the author definitely believes that ozone-related health costs vary roughly in proportion to ozone levels. As we discussed in the Answer Anticipation section, this is how the author gets from the premise that air pollution measures will reduce ozone levels by one-fifth to the conclusion that the measures will reduce the $5 billion worth of ozone-related costs by $1 billion. Moreover, this belief would strengthen the author's argument. If the costs vary in proportion to ozone levels, reducing the levels by one-fifth will also reduce the costs by one-fifth. So, this answer choice describes the author's potentially erroneous assumption, making this the correct answer.

Key Takeaway:
When the conclusion brings up a new concept that wasn't discussed in the premises, there's a good chance the argument commits a concept switch (also known as an equivocation flaw). That means the author thinks a concept discussed in the premises is roughly the same as a different concept the author brings up in the conclusion. To identify the two concepts the author thinks are linked, ask yourself which premise is at least somewhat similar to that new idea in the conclusion.

The author doesn't have to provide a reason to believe that the city will adop air pollution measure. They would have to provide such a reason if the author concluded that the city will definitely spend one billion dollars less on ozone-related health costs. But the author instead concludes that the city will spend one billion dollars less "should the proposed measures be adopted." Since the conclusion is conditioned on this hypothetical, the author doesn't have to show that the hypothetical will definitely happen. In other words, if the conclusion is "If X, then Y," the argument doesn't have to prove that X will happen.

The author never makes an emotional appeal. Emotional appeals are very rare on the LSAT. When they do appear, the author will typically conclude that we should or should not do something by invoking our fear or pity to distract us from the facts. In this case, an emotional appeal might look something like, "Even though there's no proof that the proposed air pollution measures will reduce ozone levels, we should adopt the measures. The current ozone levels disproportionally affect the city's most vulnerable citizens, and any increase in the ozone levels may prove lethal to these individuals whom our government has let down." The author doesn't do anything like that here. The author sticks to the facts about ozone levels but draws a dubious conclusion about ozone costs.

The author doesn't want to "draw attention away" from health-related costs. Their conclusion is about health-related costs! Besides, the two issues are related, as air pollution is responsible for the costs.