Passage Summary: Scientists think there might be an invisible substance in space blocking our view of stars, but a professor argues we don't need that idea because Einstein's theories already explain why we can't see them clearly.

Conclusion: There is no valid reason to accept the hypothesis that an invisible light-absorbing medium exists in outer space.

Reasoning: The phenomenon that the hypothesis was intended to explain—the low visibility of distant star systems—is already fully accounted for by the general theory of relativity.

Analysis: The professor's argument hinges on a classic 'Occam's Razor' approach, but it contains a significant logical gap. Just because one theory (General Relativity) can explain a phenomenon doesn't automatically mean a competing physical cause (the medium) doesn't exist. To make this argument hold water, the professor must assume that there is no other evidence supporting the medium's existence beyond just explaining low visibility. Look for an answer that addresses the necessity of the medium being the *only* way to explain the data or the assumption that redundant explanations are inherently false.