Passage Summary: If you can't tell a fake diamond from a real one just by looking at it, and they both look just as good, they ought to be worth the same amount.

Conclusion: Real diamonds and indistinguishable counterfeits should be considered to have the same value.

Reasoning: If two things provide the same amount of aesthetic pleasure and cannot be told apart by the naked eye, there is no reason to value one over the other.

Analysis: The author is making a normative claim about 'value' based on 'aesthetic pleasure' and 'visual appearance.' To justify this reasoning, we need a principle that explicitly links these concepts, essentially stating that value is derived only from what can be seen. The argument ignores other factors collectors care about, like rarity or origin. Look for a bridge that says if the experience of two objects is the same, their value must be the same.