The Rev. John Langan is a professor of philosophy at Georgetown University in Washington, D.C. He wrote the entry “Stem Cell Research and Religious Freedom” for Stem Cell Research: New Frontiers in Science and Ethics.

John Hyde Evans is a sociologist at the University of California, San Diego. He wrote Playing God?: Human Genetic Engineering and the Rationalization of Public Bioethical Debate and The History and Future of Bioethics: A Sociological View.

Michael M. Mendiola was associate professor of Christian ethics for the Graduate Theological Union in Berkeley, Calif. He wrote the article “Human Embryonic Stem Cells: Possible Approaches from a Catholic Perspective” for The Human Embryonic Stem Cell Debate (MIT Press, 2001). Mendiola passed away in 2008.

Dr. Irving Weissman is head of the stem cell research program at Stanford University in Palo Alto, Calif. He opposes an effort to repeal California’s law legalizing embryonic stem cell research.

Jane Maienschein is a professor of history and philosophy of science at Arizona State University in Tempe. She wrote Whose View of Life?: Embryos, Cloning, and Stem Cells (Harvard University Press, 2003).

Keith Akers is a Christian vegetarian and environmental activist who lives in Englewood, Colo. He operates the Compassionate Spirit website, which includes articles and commentary on animal welfare from a Christian perspective.

David Dion DeGrazia is a philosophy professor at George Washington University in Washington, D.C. He has written about the ethics of animal research and is the author of Animal Rights: A Very Short Introduction.

John Young is director of comparative medicine at Los Angeles Cedars-Sinai Medical Center and chairman of Americans for Medical Progress, a pro-animal testing group.

Frankie Trull is founder and president of the Foundation for Biomedical Research, an organization that promotes the responsible use of animal testing in scientific labs.