Time is a common topic in Shakespeare's sonnets, and it is used to examine aging, memory, and the fading of beauty. In "Sonnet 12," for example, the speaker says, "When I count the clock that marks the time.../Then of thy beauty do I inquire,/That thou among the wastes of time must depart." The word "time" here means "moment," and the speaker is asking whether his love will ever leave him. He knows that love grows cold over time and fears that his love will fade away forever. Shakespeare also uses time to describe what happens to people when they die. In "Sonnet 18," for example, he writes, "Th'expense of spirit in a waste of time / Is madness." This line has been interpreted to mean that spending all your time drinking and partying is insane because you are wasting your life. Finally, time is important in explaining why some sonnets are written by Shakespeare and others are not. If Shakespeare had been willing to write about his love for young women elsewhere in his works, then it would be hard to explain how many sonnets are not written by him but still fit into the sequence of 1592-1609. These include "Sonnet 110" and "Sonnet 111." Shakespeare did not want readers to know that other people wrote poems about Laura or Anne. So he invented a story - perhaps inspired by Sir Philip Sidney - in which two poets compete for the same woman.