Whether the stars have light from the sun or from themselves. They say that they have light from themselves, arguing that if Venus and Mercury did not have light from themselves, when they interpose between our eye and the sun they would darken as much of that sun as they cover from our eye. And this is false, because it is proved that a shadowy body placed within a luminous one is girdled and wholly covered by the lateral rays of the rest of that luminous body, and so it remains invisible. As is shown: when the sun is seen through the ramification of plants without leaves at a long distance, those branches occupy no part of the sun to our eyes. The same happens with the aforesaid planets, which, although they are of themselves without light, do not, as has been said, occupy any part of the sun to our eye.

Second proof.

sun - earth - moon - star. They say the stars appear most bright at night, the more they are above us, and that if they did not have light from themselves, the shadow cast by the earth interposing between them and the sun would come to darken them, they neither seeing nor being seen by the solar body. But these have not considered that the pyramidal shadow of the earth does not reach among too many stars, and for those it does reach, the pyramid is so diminished that it occupies little of the body of the star, and the rest is illuminated by the sun.