Recently, a few of our students had some questions about this Critical Reasoning problem:
Some ecologists claim that forest fires are a natural part of the ecosystem in certain types of forest environments. Botany experts support this claim, citing the fact that some plant species have adapted to survive and even thrive in fires.
Which of the following statements, if true, most strengthens the argument above?
(A) Recent campaigns to eliminate forest fires have saved thousands of plants from burning.
(B) Many forest plants have seeds that do not germinate unless exposed to intense heat and smoke.
(C) One technique used to limit the spread of forest fires is to burn the area surrounding the fire to the ground.
(D) Despite intense human intervention and innovation, huge forest fires break out every year in the United States.
(E) Some plant species release many potentially toxic chemicals into the atmosphere when burnt.
The conclusion of the statement above is the ecologists’ claim that “forest fires are a natural part of the ecosystem in certain types of forest environments.” It seems like both B and D strengthen this conclusion; I would certainly argue that this is the case. B clearly strengthens the conclusion: if the seeds of some plants cannot germinate without “intense heat and smoke,” it seems like such plant need forest fires to reproduce. D tells us that forest fires continually occur despite human attempts to prevent them: on the assumption that human intervention is not a “natural part of the ecosystem” (a questionable, though, in my opinion, allowable assumption), D also strengthens the conclusion.
So am I saying that this is a flawed question?
Of course not! If you read the question stem carefully, you are asked to strengthen the “argument.” An argument, by definition, is a conclusion supported by at least one premise. Only B strengthens the connection between the premise (that “some plant species have adapted to thrive” in forest fires) with the conclusion. D might strengthen the conclusion, but only B strengthens the argument.
This is an important distinction. Consider the following:
Some political scientists have concluded that drinking large amounts of alcohol is conducive to achieving success in electoral politics.
There is a conclusion above. But there was no argument. This is an argument:
Some sociologists have concluded that drinking large amounts of alcohol is conducive to achieving success in politics. To support this claim, they cite that Yeltsin, who drank heavily, was one of Russia’s most popular elected leaders, whereas Gorbachev, who rarely drank, never achieved electoral success.
Because the conclusion was supported by at least one premise, we can call the passage above an argument. If we were asked to strengthen the conclusion, a premise such as this would suffice:
Winston Churchill drank large amounts of alcohol, and he was one of Great Britain’s most successful prime ministers.
But the premise above would not strengthen the argument, because it does not strengthen the connection between the evidence and the conclusion. The following premise would strengthen the argument:
The majority of respondents to a recent survey claimed that they trusted Yeltsin more because they knew he was a heavy drinker.
Remember: an argument always contains a conclusion, but is defined by the presence of a conclusion supported by at least one premise.