In opposition to the cultural commons stands the ''permission culture,'' an epithet the Copy Left uses to describe the world it fears our current copyright law is creating. Whereas you used to own the CD or book you purchased, in the permission culture it is more likely that you'll lease (or ''license'') a song, video or e-book, and even then only under restrictive conditions: read your e-book, but don't copy and paste any selections; listen to music on your MP3 player, but don't burn it onto a CD or transfer it to your stereo. The Copy Left sees innovations like iTunes, Apple's popular online music store, as the first step toward a society in which much of the cultural activity that we currently take for granted -- reading an encyclopedia in the public library, selling a geometry textbook to a friend, copying a song for a sibling -- will be rerouted through a system of micropayments in return for which the rights to ever smaller pieces of our culture are doled out. ''Sooner or later,'' predicts Miriam Nisbet, the legislative counsel for the American Library Association, ''you'll get to the point where you say, 'Well, I guess that 25 cents isn't too much to pay for this sentence,' and then there's no hope and no going back.''

There is a growing sense of urgency among the members of the Copy Left. They worry that if they do not raise awareness of what is happening to copyright law, Americans will be stuck forever with the consequences of decisions now being made -- and laws being passed -- in the name of preventing piracy. ''We are at a moment in our history at which the terms of freedom and justice are up for grabs,'' Benkler says. He notes that each major innovation in the history of communications -- the printing press, radio, telephone -- was followed by a brief period of openness before the rules of its usage were determined and alternatives eliminated. ''The Internet,'' he says, ''is in that space right now.''

America has always had an ambivalent attitude toward the notion of intellectual property. Thomas Jefferson, for one, considered copyright a necessary evil: he favored providing just enough incentive to create, nothing more, and thereafter allowing ideas to flow freely as nature intended. ''If nature has made any one thing less susceptible than all others of exclusive property,'' he wrote, ''it is the action of the thinking power called an idea, which an individual may exclusively possess as long as he keeps it to himself; but the moment it is divulged, it forces itself into the possession of everyone.'' His conception of copyright was enshrined in Article 1, Section 8 of the Constitution, which gives Congress the authority to ''promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.''

But Jefferson's vision has not fared well. As the country's economy developed from agrarian to industrial to ''information,'' ideas took on greater importance, and the demand increased for stronger copyright laws. In 1790, copyright protection lasted for 14 years and could be renewed just once before the work entered the public domain. Between 1831 and 1909, the maximum term was increased from 28 to 56 years. Today, copyright protection for individuals lasts for 70 years after the death of the author; for corporations, it's 95 years after publication. Over the past three decades, the flow of material entering the public domain has slowed to a trickle: in 1973, according to Lessig, more than 85 percent of copyright owners chose not to renew their copyrights, allowing their ideas to become common coin; since the 1998 Copyright Term Extension Act lengthened present and past copyrights for an additional 20 years, little material will enter the public domain any time soon.

Some of the changes that expanded copyright protection were made with an understanding of their effects; what also troubles the Copy Left, however, are the unintended consequences of seemingly innocuous tweaks in copyright legislation. In particular, two laws that were passed years before the creation of the Internet helped set the stage for today's copyright bonanza. Before the 1909 Copyright Act, copyright was construed as the exclusive right to ''publish'' a creation; but the 1909 law changed the wording to prohibit others from ''copying'' one's creation -- a seemingly minor change that thereafter linked copyright protection to the copying technology of the day, whether that was the pen, the photocopy machine, the VCR or the Internet. In 1976, a revision to the law dispensed with the requirement of formally registering or renewing a copyright in order to comply with international copyright standards. Henceforth, everything -- from e-mail messages to doodles on a napkin -- was automatically copyrighted the moment it was ''fixed in a tangible medium.''

The true significance of these two laws didn't become apparent until the arrival of the Internet, when every work became automatically protected by copyright and every use of a work via the Internet constituted a new copy. ''Nobody realized that eliminating those requirements would create a nightmare of uncertainty and confusion about what content is available to use,'' Lessig explains, ''which is a crucial question now that the Internet is the way we gain access to so much content. It was a kind of oil spill in the free culture.''

Lessig is one of the most prominent and eloquent defenders of the Copy Left's belief that copyright law should return to its Jeffersonian roots. ''We are invoking ideas that should be central to the American tradition, such as that a free society is richer than a control society,'' he says. ''But in the cultural sphere, big media wants to build a new Soviet empire where you need permission from the central party to do anything.'' He complains that Americans have been reduced to ''an Oliver Twist-like position,'' in which they have to ask, ''Please, sir, may I?'' every time we want to use something under copyright -- and then only if we are fortunate enough to have the assistance of a high-priced lawyer.