This paper offers a provocative re-reading of the passage about the sizes of the sun, moon, and stars late in Lucretius’ De Rerum Natura (5.564-613). Attention to not only details of argumentation but also shades of meaning and contorted syntax shows a more complex, ambiguous presentation than generally acknowledged. This paper suggests that Lucretius' narrator—rather than merely parroting wrong, ridiculed doctrines—pulls student-readers into the process of inquiry. It becomes the didactic audience’s task to receive data from sense-perception and use lessons learned earlier in the poem in making correct judgments based upon that data. In Epicurean and Lucretian accounts of reality, the senses themselves are infallible; so the Lucretius-ego’s assertion that the sun as big as perceived by our senses must also be infallible. But our interpretation of what that assertion entails about the sun’s actual size is a matter of judgment, and thus fallible and uncertain indeed.