Passage Summary: An art critic argues that if the value of a piece of art doesn't come from the work itself, then any opinion about how good it is must just be a personal preference.

Conclusion: If an artwork's value is not intrinsic, then judgments about its quality are merely matters of taste.

Reasoning: The critic posits that value is either intrinsic or extrinsic; if it is not intrinsic, it must be extrinsic, which supposedly necessitates that quality judgments are subjective.

Analysis: The critic's argument hinges on a sharp divide: either value is 'intrinsic' (and thus objective) or it is 'extrinsic' (and thus subjective). To find the necessary assumption, we must identify the missing link between extrinsic value and subjectivity. The critic 'takes for granted' that extrinsic value cannot be measured or judged objectively. If there were a way to have objective standards for extrinsic value, the critic's entire logical bridge would collapse.