(Note: this is a substantially revised version of Harvard Olin Working Paper # 415 of May 2003, SSRN Abstract ID # 392202, and includes more detailed discussion of issues including the DOE, willfulness and the Knorr decision, and the FTC Report on patents and antitrust). Critics of the patent system suggest the rules for determining patentability should be stricter, subjecting patents to more scrutiny during Patent Office examination. This Article offers a counterintuitive model system under which patent applications are registered, not examined, to elucidate a new normative view that sees present positive law rules for obtaining patents as primarily operating to minimize social cost, and that accounts for otherwise puzzling aspects of the patent system. This “registration” theory for patentobtaining rules is a companion to the “commercialization” theory for patent-enforcing rules by the same author. This Article shows how these theories together offer a more coherent view of the patent system than the “reward,” “prospect,” and “rent dissipation” theories. This Article further identifies those patentability rules that are essential and those that should be reformed, while revealing inherent registration aspects of our present system and reasons for eschewing reforms presented elsewhere. * The author is 2003-2004 W. Glenn Campbell & Rita Ricardo-Campbell National Fellow and Robert Eckles Swain National Fellow at Stanford University’s Hoover Institution and Associate Professor and 2003-2004 Israel Treiman Faculty Research Fellow at Washington University School of Law. At the time this essay was first presented, he was 2001-2002 and 20022003 John M. Olin Senior Research Fellow in Law, Economics, and Business at Harvard Law School. The author gratefully acknowledges the financial support of the John M. Olin Foundation and the Washington University School of Law. He also gratefully acknowledges contributions from participants in the Fall 2003 Hoover Economics Lunch Seminar, American Law and Economics Association 2003 Annual Meeting, the Harvard Law School Visiting Scholars and Visiting Researchers 2002–2003 Colloquium, the Federal Trade Commission and Department of Justice Antitrust Division 2002 joint hearings on Competition and Intellectual Property, the 2001 Workshop Series of the John M. Olin Program in Law and Economics at the University of Chicago Law School, and the 2002 and 2001 National Lawyers Conventions of the Federalist Society for Law and Public Policy Studies, as well as the more detailed comments provided by Michael Abramowicz, John R. Allison, Kenneth Arrow, John Barton, Bernard Black, Bruce Bueno de Mesquita, Chris Bracey, Lisa English, Richard Epstein, Paul Goldstein, Wendy Gordon, Joseph Grundfest, Robert Hall, Kenneth Judd, Jay Kesan, Edward Lazear, Mark Lemley, Doug Lichtman, Clarissa Long, Jerry Marr, Rob Merges, Michael Meurer, Arie Michelsohn, Pauline Newman, Troy Paredes, Tom Pasternak, Richard Posner, Marco Quina, Randall Rader, Arti Rai, Michael Schwartz, Steve Shavell, Henry Smith, Jay Thomas, Polk Wagner, and John Witherspoon. Please send correspondence to fskieff.91@alum.mit.edu (permanent address).