Suber, Peter2010-11-092006Peter Suber, Creating an intellectual commons through open access, Understanding Knowledge as a Commons: From Theory to Practice (Charlotte Hess and Elinor Ostrom 2006). A revised version of an article first presented at the Workshop on Scholarly Communication as a Commons, Bloomington, Indiana, April 1, 2004.978-0-262-08357-70-262-08357-4http://nrs.harvard.edu/urn-3:HUL.InstRepos:4552055Open-access (OA) literature is online, free of charge, and free of most copyright and licensing restrictions. The low-hanging fruit for OA is literature that authors consent to distribute without payment, or for which they are paid salaries by their employers rather than royalties by their publishers. This relatively small but very important category of literature includes peer-reviewed journal articles and their preprints, the primary literature of science. In this paper I discuss the peculiarities of royalty-free literature, the conditions that lead authors to consent to OA (including authors of loyalty-producing literature), and some obstacles to an OA commons that have the flavor of a tragedy of the commons.en-USscholarly communicationMonograph or Book2010-11-0910.1038/ngeo450