Jewel collectors, fearing that their eyes will be deceived by a counterfeit, will not buy a diamond unless the dealer guarantees that it is genuine. But why should a counterfeit give any less aesthetic pleasure when the naked eye cannot distinguish it from a real diamond? Both jewels should be deemed of equal value.
Summary: Counterfeit does not give less aesthetic pleasure. Therefore, equal value.
GAP is aesthetic pleasure to equal value. So need to find an answer choice that bridges this gap.
Which one of the following principles, if valid, most helps to justify the reasoning in the argument above?
(A) Jewel collectors should collect only those jewels that provide the most aesthetic pleasure.
Argument's reasoning is not about collecting jewels. Irrelevant.
(B) The value of a jewel should depend at least partly on market demand.
Market demand is out of scope
(C) It should not be assumed that everyone who likes diamonds receives the same degree of aesthetic pleasure from them.
liking diamond and receiving aesthetic pleasure is not discussed in the passage.
(D) The value of a jewel should derive solely from the aesthetic pleasure it provides.
Yes, it bridges the gap. So if value depends solely on aesthetic pleasure, no less aesthetic pleasure will imply both are of equal value. Correct
(E) Jewel collectors should not buy counterfeit jewels unless they are unable to distinguish counterfeit jewels from real ones.
if they able to distinguish -- buy counterfeit is what this sentence implies, this does not justify the reasoning about equal value.