In sonnet 31 of Sir Philip Sidney’s Astrophil and Stella sonnet sequence, Astrophil extensively compares his own feelings about Stella with the feelings of the moon. Such an extended comparison was known in Sidney’s period as a “conceit.” The problem with Astrophil’s comparison, of course, is that the moon has no feelings. It lacks consciousness and thus cannot feel anything. It is typical of Astrophil, however, to project his own feelings onto other things and other people. He is so infatuated with his desire for Stella that he does not think clearly or rationally. The feelings and thoughts that are most important to him are his own. No wonder, then, that he projects those thoughts and feelings even onto a piece of rock in the sky!
Astrophil begins be asserting that the moon seems sad because it is moving slowly into the sky. Of course, the moon feels nothing, and, besides, it moves (or appears to move) at the same pace night after night, never changing its speed at all. Indeed, one of the great paradoxes about the moon (as far as people in the Renaissance were concerned) is that it is entirely predictable while also seeming to be constantly changing. It moves through the sky in a completely regular, reliable way, and yet its “face” is constantly in motion, from fully bright and completely circular to the opposite (from a “full moon” to a “new moon”). For this reason, the moon was a prime symbol in the Renaissance of mutability, or constant change. The earth, which seems to lie beneath the moon, was called the “sublunary” realm (the realm beneath the moon), because the earth was also constantly changing. People who seemed unstable and full of change were called “lunatics.” A case can be made, in fact, that Astrophil is a bit of a lunatic himself, because his fixation on Stella had greatly unsettled his mind.
Astrophil believes that he and the moon have much in common: they both feel sad, they both move slowly because of their sadness, and they both have pale faces as a result of their mutual sadness. In reality, of course, none of this is true about the moon, however true it may be about Astrophil. Astrophil wonders if Cupid, the god of irrational desire, has afflicted the moon in the same way that Astrophil feels victimized by Cupid:
Sure, if that long with Love acquainted eyes
Can judge of Love, thou feel’st a lover’s case;
I read it in thy looks; thy languish’d grace
To me that feel the like, thy state descries.
In other words, Astrophil says that since he knows how it feels to be in love (actually, full of selfish desire), he knows exactly how the moon is feeling. This poem provides a textbook example of how a prideful, self-centered person can let his own strong emotions color his thinking and make it literally irrational. Sidney is having fun with Astrophil here, as he has fun with him throughout the entire sequence. Sidney creates, in Astrophil, a comical alter ego whose very foolishness highlights Sidney’s own wisdom.
At the very end of the poem, Astrophil concedes that Stella (and others) believe that he is lacking in “wit” (that is, wisdom) because of his obsession with her. He also wonders if the objects of the moon’s affections (in fact, there are none) are also proud and tormenting as Astrophil believes Stella is. The entire poem illustrates Astrophil’s comical irrationality in comparing himself to the moon.