If I drop dead tomorrow, all the work I've produced since 1978 will enjoy copyright protection for the next 70 years, until 2072, some 120 years after my birth. If I live another 30 years or so all the work I've produced since 1978 will be protected into the beginning of the twenty-second century. Much as I value my copyrights, which allow me to control and profit from my work, and much as I disdain plagiarism and pirating, I don't expect to derive any benefit from copyrights that survive me by decades. But, then again, the Copyright Extension Act of 1998, which added an additional 20 years to almost all existing copyrights, wasn't intended to benefit me or other individual writers and artists. It was primarily intended to benefit corporations that expect to live forever, with congressional assistance: Disney may prove virtually immortal, if it never loses the rights to Mickey Mouse.

Disney lobbied hard for the 1998 law, partly because Mickey's copyright was due to expire in 2003. Now it will last an additional 20 years, until 2023, or the expiration of the next copyright extension -- whichever comes second. Can Congress repeatedly extend copyrights for decades, impoverishing the public domain, to benefit corporations and the distant descendants of individual creators? That question is now before the Supreme Court: In Eldred v. Ashcroft, it agreed to review the constitutionality of the 1998 copyright-extension law.

The law has been challenged by a group of nonprofit organizations and businesses that use works in the public domain. The lead plaintiff, Eric Eldred, operates Eldred Press, which posts literary works by authors such as Nathaniel Hawthorne on the Internet. Eldred and his co-plaintiffs are represented by an impressive array of lawyers, including Stanford University professor Larry Lessig, and Charles Nesson and Jonathan Zittrain of Harvard Law School's Berkman Center for Internet and Society. All have a strong ideological commitment to preventing new technologies from destroying the traditional balance between the intellectual property rights of creators and unrestricted dissemination of information, ideas, and entertainment.

The notion that creators should be granted exclusive, but temporary rights in their work is enshrined in the Constitution. The copyright and patent clause gives Congress the power to grant authors and inventors exclusive rights to their work "for limited times," in order to ensure artistic and scientific progress. Temporal limits on copyrights strike an essential compromise between the rights of creators and the public's interest in their creations. Depriving individuals of all rights to their work leaves them with little incentive to produce it; permanently depriving the public of any right to use the work freely is antithetical to democratic faith in a marketplace of ideas.

Eldred v. Ashcroft focuses on the constitutional mandate that copyrights last only for "limited times." Originally copyrights were relatively brief; pursuant to the Copyright Act of 1790, they lasted a maximum of 28 years. Copyrights were then extended by Congress repeatedly; under the 1976 law, copyrights lasted the author's lifetime plus 50 years; works for hire (like Mickey Mouse) lasted 75 years from the year of publication or 100 years from the date of creation, whichever came first. Given the extraordinary life of copyrights today, and the effect of their longevity on public access to music, literature, and other intellectual properties, Congress has arguably violated the Constitution by granting effectively unlimited copyrights. Like leases with automatic renewal clauses, copyrights may never terminate.

In issuing unlimited copyrights, Congress is also arguably subverting the intent of the copyright clause: to provide for artistic progress. Fewer works will be created under a system of endless copyrights. There's no reason to believe that people would be deterred from creating new works if copyrights lasted "only" for the duration of their lifetimes, or lifetimes plus 50 years. But the longer copyrights last, the less likely that other people inspired by the copyrighted work will use it to create new works, like The Wind Done Gone, the recent parody of Gone with the Wind that Margaret Mitchell's heirs attempted unsuccessfully to suppress. Indeed, Disney's use of works in the public domain, like Cinderella or Winnie-the-Pooh, which recently generated an estimated $4.5 billion of annual income for Disney and its licensees -- testifies to the importance of a rich public domain in inspiring new creations.

What inspires and sustains writers and artists? The opportunity to profit from your work matters greatly, of course. Only people with more money than imagination think that artists benefit from the daily stress of poverty. But in general, the creation of art and literature is not terribly remunerative. On an hourly basis, I've probably made little more than a minimum wage through much of my writing career. For me, the value of copyrights often lies mainly in the control they allow me to exert over my work: No one can publish or alter it, anywhere or in any way, for any purpose, without my permission.

But a copyright that lasts my lifetime would give me all the rights to my work that I need, or could use. And, during my lifetime, I might derive some psychic benefit from knowing that after my death my work would be publicly available, without restriction. Why do writers and artists create? Their reasons vary, of course. I write partly out of an irresistible impulse to hold forth -- for the sheer pleasure of expressing and communicating ideas -- partly for the satisfaction of being credited and recognized for my work, partly to persuade people, and partly to provoke public conversations and consideration of ideas. I'm frustrated when readers misinterpret my work and invigorated when they interpret it unpredictably. I don't believe in an afterlife, but I suspect that my work would survive if my copyrights died with me.