VyshakhR1995 wrote:
Opponents of peat harvesting in this country argue that it would alter the ecological balance of our peat-rich wetlands and that, as a direct consequence of this, much of the country’s water supply would be threatened with contamination. But this cannot be true, for in Ireland, where peat has been harvested for centuries, the water supply is not contaminated. We can safely proceed with the harvesting of peat.
Which one of the following, if true, most strengthens the argument?
(A) Over hundreds of years, the ecological balance of all areas changes slowly but significantly, sometimes to the advantage of certain flora and fauna.
(B) The original ecology of the peat-harvesting areas of Ireland was virtually identical to that of the undisturbed wetlands of this country.
(C) The activities of the other industries in coming years are likely to have adverse effects on the water supply of this country.
(D) The peat resources of this country are far larger than those of some countries that successfully harvest peat.
(E) The peat-harvesting industry of Ireland has been able to supply most of that country’s fuel for generations.
Source: LSAT PrepTest 30 Q#3
The author’s conclusion is that we can safely proceed with the harvesting of peat. How do we know that, contrary to opponents’ claims, such harvesting will not threaten our water supply? Easy, according to the author: because in Ireland they have been harvesting peat for centuries and the water supply is not contaminated. Do you see what’s going on here? It’s simple: The author is reasoning by analogy—harvesting peat in this country will be safe because harvesting peat in Ireland is safe. Once you identified that the author argues by analogy, you should have been able to predict that the correct answer would tell you something about how Ireland and this country are similar. And that’s exactly what (B) does, telling you that the ecology of peat harvesting areas in Ireland is identical to the ecology of wetlands in this country.
(A) tells us that environments change, but that tells us nothing about the similarity between Ireland and this country that’s necessary for this argument by analogy to work.
(C) is outside the scope because we aren’t concerned with the effect of other industries on the water supply. We only want to know what effect peat harvesting will have.
(D) is irrelevant, since it doesn’t compare this country to Ireland, which is after all the relevant “other country.” If any- thing, (D) might be a weakener, since it points out a potentially relevant difference between this country and other countries. In any case, (D) is no strengthener.
(E) is irrelevant. We’re not concerned with peat harvesting as a source of fuel; we want to know about its effects on the water supply.
•
In arguments by analogy, the classic way to strengthen the argument is by showing how the two things that are being compared are similar to each other; the classic way to weaken these arguments is by showing how the two entities are different from each other.