PrepTest 146, Section 1, Question 21
Most kinds of soil contain clay, and virtually(35 more words not shown)
The pattern of flawed reasoning(16 more words not shown)
- AMost pharmacies sell(32 more words not shown)
- BUndoubtedly, most pharmacies(32 more words not shown)
- CMost pharmacies sell(32 more words not shown)
- DVirtually every pharmacy(30 more words not shown)
- ENearly all pharmacies(32 more words not shown)
Reading the argument
What if all those soils contain sand and none contains organic material? They would still satisfy 'sand or organic material, or both.' That statement doesn't require the options to be evenly distributed—or even require both options to occur.
Think about saying that virtually every person has eyes or a tail. Even in an imagined group where everyone has eyes and nobody has a tail, that statement is true. It wouldn't let us conclude that some people have tails. Likewise, most soils could contain clay and virtually all could contain sand, leaving no soil with both clay and organic material.
What we’re looking for
The parallel needs all those moving parts: most members of a group have one feature, nearly all have either of two other features, and the conclusion insists that the first feature overlaps with each of the other two. That's the unsupported step. The first feature could overlap with only one of them.
Working the answers
- A
The premises match well: pharmacies replace soils, cosmetics replace clay, and shampoo and toothpaste replace sand and organic material. But the conclusion doesn't simply assert that both overlap groups exist. It says if one overlap exists—cosmetics with toothpaste—then the other must exist too. That conditional claim differs from the original's direct assertion that there are members of both groups.
- B
This makes 'most pharmacies sell cosmetics' the conclusion. In the original, the corresponding statement that most soils contain clay is a starting premise. B also uses the existence of the two overlap groups as evidence, whereas the original is trying to establish those groups. The same kinds of statements appear, but they do different jobs.
- C
This says that if there are no pharmacies selling both cosmetics and toothpaste, there must be some selling both cosmetics and shampoo. It doesn't insist that both overlaps exist. It allows the cosmetics sellers to fall on just one side of the shampoo-or-toothpaste division—the very possibility the original overlooks. The conclusion is therefore different in substance, not merely because it uses 'unless.'
- D
The first premise says shampoo sellers also sell toothpaste. That links the two products to each other. The original instead says virtually all soils have one of two features or both; it doesn't say having sand generally brings organic material along with it. D starts from a different relationship even though its conclusion mentions the same two overlaps.
- ECorrect
Pharmacies are soils; cosmetics are clay; toothpaste and shampoo are the two alternatives, organic material and sand. Nearly all pharmacies sell at least one of those alternatives, and most sell cosmetics. The conclusion claims there are pharmacies combining cosmetics with each alternative.
But all the cosmetics sellers could sell shampoo and none could sell toothpaste. That would satisfy the premises and defeat one half of the conclusion, just as the soils could all have sand and none could have organic material. The order of the premises changes, but their jobs and the unsupported conclusion match.
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