Gibson's law

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In public relations,[1] and in the practice of law, Gibson's law holds that "For every PhD there is an equal and opposite PhD."[2] The term specifically refers to the conflict between testimony of expert witnesses called by opposing parties in a trial under an adversarial system of justice.[3] It is also applied to conflicting scientific opinion injected into policy decisions by interested parties creating a controversy to promote their interests.[4]

See also[edit]

  • Clarke's three laws, including Clarke's fourth law: "For every expert there is an equal and opposite expert."


  1. ^ Proctor, Robert .N. (2004). "Should medical historians be working for the tobacco industry?". The Lancet. 363 (9416): 1174–1175. doi:10.1016/S0140-6736(04)15981-3. PMID 15081644. Retrieved 2007-08-05. There is a saying in American public-relations circles that for every PhD there is an equal and opposite PhD
  2. ^ Lewontin, Richard C.; Singh, Rama S. (2001). Thinking about evolution: historical, philosophical, and political perspectives. Volume two. Robert N. Proctor. Cambridge, UK: Cambridge University Press. p. 568. ISBN 0-521-62070-8. 'For every Ph.D. there is an equal and opposite Ph.D.' Gibson's Law
  3. ^ Zingrone, N. (March 2002). "Controversy and the problems of parapsychology". Journal of Parapsychology. 66 (19): 3. Retrieved 2007-08-05. ...controversy flows from a "truth" that encapsulates the ease with which both prosecuting attorneys and defense attorneys can always find a crucial and credible scientific expert to testify on behalf of their own case and against the crucial and credible scientific expert hired by their opponents
  4. ^ Hess, David J. (1997). Science studies: an advanced introduction. New York: New York University. p. 94. ISBN 0-8147-3564-9. Proctor borrowed “Gibson's law” from public relations research and introduced the term “smokescreen effect” as two important techniques for inducing controversy to promote interests.