In economics, a public good is a good that is both non-excludable and non-rivalrous in that individuals can not be effectively excluded from use and where use by one individual does not reduce availability to others. Examples of public goods include fresh air, clean water, knowledge, lighthouses, open source software, radio and television broadcasts, roads, street lighting. Public goods that are available everywhere are sometimes referred to as global public goods.

In the real world, many public goods may at times be subject to excessive use resulting in negative externalities affecting all users; for example air pollution and traffic congestion. Public goods problems are often closely related to the "free-rider" problem or the tragedy of the commons. Public goods may also become subject to restrictions on access and may then be considered to be club goods or private goods; exclusion mechanisms include copyright, patents, congestion pricing and pay television.

Uncoordinated markets driven by self-interested parties may be unable to provide these goods. There is a good deal of debate and literature on how to measure the significance of public goods problems in an economy, and to identify the best remedies.

Terence Kealey is the current Vice-Chancellor of the University of Buckingham, Britain's only private university. Prior to his tenure at Buckingham, Kealey lectured in clinical biochemistry at Cambridge University. He is well known for his outspoken opposition to public funding of science.

Frederick Antony Ravi Kumar Zacharias (born 1946) is an Indian-born, Canadian-American evangelical Christian apologist. Zacharias is the author of numerous Christian books, including Gold Medallion Book Award winner Can Man Live Without God? and bestsellers Light in the Shadow of Jihad and The Grand Weaver. He is the founder and chairman of the board of Ravi Zacharias International Ministries, host of the radio programs Let My People Think and Just Thinking, and visiting professor at Wycliffe Hall of Oxford, where he teaches apologetics and evangelism. Zacharias studied as a visiting scholar at Cambridge University and held the chair in Evangelism and Contemporary Thought at Alliance Theological Seminary from 1981 to 1984. Commentator Chuck Colson referred to Zacharias as "the great apologist of our time."

Zacharias was born in Madras, India. Zacharias claims descent from a woman (of the Nambudiri Brahmin caste) and a low caste Boatman. Missionaries spoke to one of his ancestors about Christianity and thereafter the family was converted. Zacharias grew up in a nominal Anglican household, and he himself was an atheist until the age of 17, when he unsuccessfully tried to commit suicide by swallowing poison. While in the hospital, a local Christian worker brought him a Bible and instructed his mother to read to him out of John 14. Zacharias says that it was John 14:19 that touched him and caused him to commit his life to Christ.

Mark Gerald Kingwell, M.Litt, M.Phil, PhD, D.F.A. (born March 1, 1963) is a Canadian professor of philosophy and associate chair at the University of Toronto's Department of Philosophy. Kingwell is a fellow of Trinity College. He specialises in theories of politics and culture.

Kingwell has published twelve books, most notably, A Civil Tongue: Justice, Dialogue, and the Politics of Pluralism, which was awarded the Spitz Prize for political theory in 1997. In 2000 Kingwell received an honorary Doctor of Fine Arts from the Nova Scotia College of Art and Design, for contributions to theory and criticism. He has held visiting posts at institutions including: University of Cambridge, University of California at Berkeley, and City University of New York where he held the title of Weissman Distinguished Professor of Humanities.

He studied at the University of Toronto, editing The Varsity through 1983 to 1984 and the University of Toronto Review from 84-85. He received his BA degree from St. Michael's College with High Distinction in 1985, his MLitt degree from the University of Edinburgh in 1987, and both his M.Phil and PhD degrees from Yale University in 1989 and 1991 respectively. He was married to Gail Donaldson in 1988. The marriage ended in divorce in 2004.

Diane Silvers Ravitch (born July 1, 1938) is an historian of education, an educational policy analyst, and a research professor at New York University's Steinhardt School of Culture, Education, and Human Development. Previously, she was a U.S. Assistant Secretary of Education

Ravitch began her career as an editorial assistant at the New Leader magazine, a small journal devoted to democratic ideas. In 1975, she became a historian of education with a Ph.D. from Columbia University. At that time she worked closely with Teachers College president Lawrence A. Cremin, who was her mentor.

She was appointed to public office by Presidents George H. W. Bush and Bill Clinton. Secretary of Education Richard Riley appointed her to serve as a member of the National Assessment Governing Board, which supervises the National Assessment of Educational Progress; she was a member of NAGB from 1997 to 2004.

She has participated in a "blog debate" called "Bridging Differences" with Steinhardt School colleague Deborah Meier on the website of Education Week since February 26, 2007.