Post-normal science (PNS) represents a novel approach for the use of science on issues where "facts [are] uncertain, values in dispute, stakes high and decisions urgent". PNS was developed in the 1990s by Silvio Funtowicz and Jerome R. Ravetz. It can be considered as a reaction to the styles of analysis based on risk and cost-benefit analysis prevailing at that time, and as an embodiment of concepts of a new "critical science" developed in previous works by the same authors. In a more recent work PNS is described as "the stage where we are today, where all the comfortable assumptions about science, its production and its use, are in question".
In 1962, Thomas Kuhn's The Structure of Scientific Revolutions introduced the concept of normal science as part of his theory that scientific knowledge progresses through socially constructed paradigm shifts, where normal science is what most scientists do all the time and what all scientists do most of the time. The process of a paradigm shift is essentially as follows:
- from normal science (the rules are agreed upon or disagreed upon in debates that cannot be concluded; science is puzzle solving, but some contradictions in theory cannot be resolved)
- to revolutionary science (important rules are called into question; contradictions may be resolved; paradigms shift)
- to new normal science (new rules are accepted, science returns to puzzle solving under new rules).
An illustration of the theory in practice is the Copernican revolution, where Copernicus’ idea of a (sun-centered) solar system was largely ignored (not in the rules) when first introduced; then Galileo was deemed a heretic for supporting the idea (rules called into question); and finally, after a revolution in cosmology, the solar system became an obvious and foundational part of scientific knowledge (new rules).
Another example is the question of whether light is a particle or a wave. For a long time there was debate on this point. Advocates on both sides had many valid arguments based on scientific evidence but were lacking a theory that would resolve the conflict. After a revolution in thinking, it was realized that both perspectives could be true.
Physicist and policy adviser James J. Kay described post-normal science as a process that recognizes the potential for gaps in knowledge and understanding that cannot be resolved in ways other than revolutionary science. He argued that (between revolutions) one should not necessarily attempt to resolve or dismiss contradictory perspectives of the world, whether they are based on science or not, but instead incorporate multiple viewpoints into the same problem-solving process. From the ecological perspective post-normal science can be situated in the context of 'crisis disciplines' – a term coined by the conservation biologist Michael E. Soulé to indicate approaches addressing fears, emerging in the seventies, that the world was on the verge of ecological collapse. In this respect Michael Egan defines PNS as a 'survival science'. More recently PNS has been defined as a movement of ‘informed critical resistance, reform and the making of futures’  .
Moving from PNS Ziauddin Sardar developed the concept of Postnormal Times (PNT). Sardar was the editor of FUTURES when it published the article ‘Science for the post-normal age’ presently the most cited paper of the journal. A recent review of academic literature conducted on the Web of Science and encompassing the topics of Futures studies, Foresight, Forecasting and Anticipation Practice  identifies the same paper as "the all-time publication that received the highest number of citations".
"At birth Post-normal science was conceived as an inclusive set of robust insights more than as an exclusive fully structured theory or field of practice". Some of the ideas underpinning PNS can already be found in a work published in 1983 and entitled "Three types of risk assessment: a methodological analysis"  This and subsequent works  show that PNS concentrates on few aspects of the complex relation between science and policy: the communication of uncertainty, the assessment of quality, and the justification and practice of the extended peer communities.
Coming to the PNS diagram (figure above) the horizontal axis represents ‘Systems Uncertainties’ and the vertical one ‘Decision Stakes’. The three quadrants identify Applied Science, Professional Consultancy, and Post-Normal Science. Different standards of quality and styles of analysis are appropriate to different regions in the diagram, i.e. Post-normal science does not claim relevance and cogency on all of science's application but only on those defined by the PNS's mantram with a fourfold challenge: ‘facts uncertain, values in dispute, stakes high and decisions urgent’. For applied research science’s own peer quality control system will suffice (or so was assumed at the moment PNS was formulated in the early nineties), while professional consultancy was considered appropriate for these settings which cannot be ‘peer-reviewed’, and where the skills and the tacit knowledge of a practitioner are needed at the forefront, e.g. in a surgery room, or in a house on fire. Here a surgeon or a fireman takes a difficult technical decision based on her or his training and appreciation of the situation (the Greek concept of ‘Metis’).
There are important linkages between PNS and complexity science, e.g. system ecology (C. S. Holling) and hierarchy theory (Arthur Koestler). In PNS, complexity is respected through its recognition of a multiplicity of legitimate perspectives on any issue; and reflexivity is realised through the extension of accepted ‘facts’ beyond the supposedly objective productions of traditional research. Also, the new participants in the process are not treated as passive learners at the feet of the experts, being coercively convinced through scientific demonstration. Rather, they will form an ‘extended peer community’, sharing the work of quality assurance of the scientific inputs to the process, and arriving at a resolution of issues through debate and dialogue. The necessity to embrace complexity in a post normal perspective to understand and face zoonoses is argumented by David Waltner-Toews.
Extended Peer Community
PNS concept of extended peer community moves from and transcends the familiar concept of scientific peer community relative to a well-defined field of scientific research. The peer community is extended in two respects: first, more than one discipline is assumed to have a potential bearing on the issue being debated, thereby providing different lenses to consider the problem. Second the community is extended to lay actors, taken to be all those with stakes, or an interest, in the given issue. Perhaps the best justification of the concept is offered by Paul Feyerabend in Against Method . For Feyerabend the participation of experts together with non-experts would allow the citizens to mature, inter alia by realizing that the experts are themselves lay-people outside their restricted field of competence. For Giandomenico Majone  "In any area of public policy the choice of instruments, far from being a technical exercise that can be safely delegated to the experts, reflects as in a microcosm all the political, moral, and cultural dimensions of policy-making." The same author notes: "Dialectical confrontation between generalists and experts often succeeds in bringing out unstated assumptions, conflicting interpretations of the facts, and the risks posed by the projects". These considerations justifies the need for an extended peer community, as the arena where the policy instruments and options can be discussed with - but without deference to - the experts and the authorities.
The lay members of the community thus constituted may also take upon themselves active 'research' tasks; this has happened e.g. in the so-called 'popular epidemiology' , when the official authorities have shown reticence to perform investigations deemed necessary by the communities affected - for example - by a case of air or water pollution  , and more recently ‘citizen science’ . The extended community can usefully investigate the quality of the scientific assessments provided by the experts, the definition of the problem, as well as research priorities and research questions .
Thus, the extension of the peer community is not only ethically fair or politically correct, but also enhances the quality of the relevant science. An example is provided by Brian Wynne, who discusses the Cumbrian sheep farmers' interaction with scientist and authorities in the relation to the Chernobyl radioactive fallout .
The concept of extended peer community was developed in the context of politicised quality controversies in science (such as 'housewife' or 'popular' epidemiology ), early evidence-based medicine (the Cochrane collaboration), and the total quality management ideas of W. Edwards Deming, in particular quality circles.
Beside its dominating influence in the literature on 'futures', PNS is considered to have influenced the ecological ‘conservation versus preservation debate’, especially via its reading by American pragmatist Bryan G. Norton. According to Jozef Keulartz  the PNS concept of "extended peer community" influenced how Norton's developed his 'convergence hypothesis'. The hypothesis posits that ecologists of different orientation will converge once they start thinking 'as a mountain', or as a planet. For Norton this will be achieved via deliberative democracy, which will pragmatically overcome the black and white divide between conservationists and preservationists. More recently it has been argued that conservation science, embedded as it is in a multi-layered governance structures of policy-makers, practitioners, and stakeholders, is itself an 'extended peer community', and as a result conservation has always been ‘post-normal’ .
Other authors  attribute to PNS the role of having stimulated the take up of transdisciplinary methodological frameworks, reliant on the social constructivist perspective embedded in PNS.
Today Post-normal science is intended as applicable to most instances where the use of evidence is contested due to different norms and values.
As summarized in a recent work "the ideas and concepts of post normal science bring about the emergence of new problem solving strategies in which the role of science is appreciated in its full context of the complexity and the uncertainty of natural systems and the relevance of human commitments and values.
For Peter Gluckman (2014), chief science advisor to the Prime Minister of New Zealand, post normal science approaches are today appropriate for a host of problems including "eradication of exogenous pests […], offshore oil prospecting, legalization of recreational psychotropic drugs, water quality, family violence, obesity, teenage morbidity and suicide, the ageing population, the prioritization of early-childhood education, reduction of agricultural greenhouse gases, and balancing economic growth and environmental sustainability". For Carrozza  PNS can be "framed in terms of a call for the ‘democratization of expertise’", and as a "reaction against long-term trends of ‘scientization’ of politics—the tendency towards assigning to experts a critical role in policymaking while marginalizing laypeople". For Mike Hulme (2007), writing on The Guardian Climate change seems falls into the category of issues which are best dealt with in the context of PNS and notes that "Disputes in post-normal science focus as often on the process of science - who gets funded, who evaluates quality, who has the ear of policy - as on the facts of science". Recent reviews of the history and evolution of PNS, its definitions, conceptualizations, and uses can be found in Turnpenny et al., 2010, and in The Routledge Handbook of Ecological Economics (Nature and Society). There has been recently an increased reference to post-normal science, e.g. in Nature (journal).
A criticism of post-normal science is offered by Weingart (1997) for whom Post-normal science does not introduce a new epistemology but retraces earlier debates linked to the so-called "finalization thesis". For Jörg Friedrichs  – comparing the issues of climate change and peak energy – an extension of the peer community has taken place in the climate science community, transforming climate scientists into ‘stealth advocates’ , while scientists working on energy security – without PNS, would still maintain their credentials of neutrality and objectivity.
The journal FUTURES devoted several specials issues to PNS.
- The first was in 1999 and included as editorial two pieces: from Jerome Ravetz and Silvio Funtowicz, Post-Normal Science—an insight now maturing, and from Jerome Ravetz: What is Post-Normal Science.
- The second special issue, edited by Merryl Wyn Davies, was entitled "Post normal times" in 2011. This was a selection of papers from the symposium "Post Normal Science – perspectives & prospectives 26-27th June 2009, Oxford." A summary of the abstracts can be found on the NUSAP net.
- The third special issue on PNS was in 2017. This special issue contains a selection of papers discussed at the University of Bergen's Centre for the Study of the Sciences and the Humanities between 2014 and 2016. The issue includes also two extended commentaries on the present crisis in science and the post-fact/post-truth discourse, one from Europe (Saltelli and Funtowicz) and one from Japan (Tsukahara). All articles in this special issue are in open access.
More titles and links relative to PNS special issues are available at the NUSAP net.
The crisis of science
It has been argued  that PNS scholars have been prescient in anticipating the present crisis in science's quality control and reproducibility. A group of scholars of PNS orientation has published in 2016 a volume on the topic , discussing inter alia what this community perceive as the root causes of the present science's crisis.
Among the quantitative styles of analysis which make reference to post-normal science one can mention NUSAP for numerical information, sensitivity auditing for indicators and mathematical modelling and MUSIASEM in the field of social metabolism.
In relation to mathematical modelling PNS suggests a participatory approach, whereby ‘models to predict and control the future’ are replaced by ‘models to map our ignorance about the future’, in the process exploring and revealing the metaphors embedded in the model.  PNS is also known for the its definition of GIGO: in modelling GIGO occurs when the uncertainties in the inputs must be suppressed, lest the outputs become completely indeterminate. 
Videos from the 3rd Post-normal Science Symposium, September 2017, Tübingen.
Videos from the 4th Post-normal Science Symposium, November 2018, Barcelona.
Lecture of Silvio Funtowicz: Post Normal Science: Exploring Collective Accountability, 6 March 2019, Trento.
- Science for Policy: Post-Normal Science in Practice, (PNS_1) December 10-11 2014 Bergen (NO)
- New Currents in Science: The Challenges of Quality, (PNS_2) March 3-4 2016 Ispra
- ‘Post-truth’ and a crisis of trust? Perspectives from post-normal science and extended citizen participation, (PNS_3) Tübingen, 25/26 September 2017.
- Science as a movement: between informed critical resistance, reform and the making of futures, 4th international symposium on Post Normal Science, (PNS_4) Barcelona, 15/17 November 2018.
- SCIENCE - POST NORMAL PERSPECTIVES: Jerry Ravetz at 90, a workshop of the Institute for Science, Innovation and Society to honour Jerome R. Ravetz 90th birthday. May 31st, 2019, Oxford.
- Future event: 5th Symposium of Post Normal Science (PNS_5), "Knowledge, Science Practices and Integrity: Quality through a Post-Normal Science Lens", University of Florence (Florence, IT), Palazzo Fenzi-Maruccelli, 21-23 September 2020.
It has been noted that the framings of these PNS events address the concerns of practicing scientists in the post-truth era, where science is confronted with ‘alternative facts’ and open to gross political interference and interpretation.
- Funtowicz, S. and Ravetz, J., 1993. "Science for the post-normal age", Futures, 31(7): 735-755.
- Funtowicz, S. O. and Ravetz, J. R., 1991. "A New Scientific Methodology for Global Environmental Issues", in Costanza, R. (ed.), Ecological Economics: The Science and Management of Sustainability: 137–152. New York: Columbia University Press.
- Funtowicz, S. O. and Ravetz, J. R., 1992. "Three types of risk assessment and the emergence of postnormal science", in Krimsky, S. and Golding, D. (eds.), Social theories of risk: 251–273. Westport, Connecticut: Greenwood.
- Funtowicz, S. and Ravetz, J., 1990. Uncertainty and quality in science for policy. Dordrecht: Kluwer Academic Publishers.
- Ravetz, J. R., 1971. Scientific Knowledge and its Social Problems. Oxford University Press.
- Ravetz, J.R., 2006, The No nonsense guide to science, New Internationalist.
- Egan, M., 2018, Survival Science: Crisis Disciplines and the Shock of the Environment in the 1970s, Centaurus 2018: doi:10.1111/1600-0498.12149.
- J. R. Ravetz, “Post-Normal Science Symposium: Address by Jerome Ravetz Reflections on ‘informed critical resistance, reform and the making of futures,’” University of Oxford, Institute for Science, Innovation and Society, 2018. [Online]. Available: https://www.insis.ox.ac.uk/article/post-normal-science-symposium-address-jerome-ravetz.
- Thomas Gauthier, Sylvaine Mercuri Chapuis, 2018, An Investigation of Futures Studies Scholarly Literature, In: Poli R. (eds) Handbook of Anticipation. Springer, Cham
- Funtowicz, S., 2016, personal correspondence.
- Funtowicz, S. O. and Ravetz, J. R. (1985), Three types of risk assessment: a methodological analysis, in C. Whipple and V. T. Covello (Eds), Risk Analysis in the Private Sector, pp 217-232 (Plenum, New York).
- Rees, M., 2017, Black holes are simpler than forests and science has its limits, AEON, 01 December.
- Funtowicz, S., and Ravetz, J.R., THE POETRY OF THERMODYNAMICS, Energy, entropy/exergy and quality, Futures, Vol. 29, No. 9. pp. 791-810, 1997.
- Waltner-Toews D. 2017, Zoonoses, One Health and complexity: wicked problems and constructive conflict. Phil. Trans. R. Soc. B 372.
- Feyerabend, P. (1975). Against method. Verso.
- Majone, G. (1989). Evidence, argument, and persuasion in the policy process. Yale University Press.
- Brown, P. (1997). Popular Epidemiology Revisited. Current Sociology, 45(3), 137–156.
- Fjelland, R. (2016). When Laypeople are Right and Experts are Wrong: Lessons from Love Canal. International Journal for Philosophy of Chemistry, 22(1), 105–125.
- Stilgoe, J. (2009). Citizen Scientists: Reconnecting Science with Civil Society. London: Demos.
- Miedema, F. (2016, May 12). To confront 21st century challenges, science must rethink its reward system | Science | The Guardian. The Guardian.
- Wynne, B. (1992). Misunderstood misunderstanding: social identities and public uptake of science. Public Understanding of Science, 1, 281–304.
- Phil Brown, 1997, Popular Epidemiology Revisited, Current Sociology, Volume: 45 issue: 3, page(s): 137-156.
- Keulartz, J. (2018). Does Deliberation Promote Ecological Citizenship? The Convergence Hypothesis and the Reality of Polarization. In S. Sarkar & B. A. Minteer (Eds.), A Sustainable Philosophy—The Work of Bryan Norton, The International Library of Environmental, Agricultural and Food Ethics 26. Springer.
- Rose, David Christian, 2018, Avoiding a Post-truth World: Embracing Post-normal Conservation, Conservation and Society, Vol. 16, Issue 4, p. 518-524.
- Heaslip, E., & Fahy, F. (2018). Developing transdisciplinary approaches to community energy transitions: An island case study. Energy Research & Social Science.
- Lister, A. R., Ingram, J. C., Briehl, M. M., & Diana, S. (2018). THE BIOACCUMULATION OF URANIUM IN SHEEP HEART AND KIDNEY: THE IMPACT OF CONTAMINATED TRADITIONAL FOOD SOURCES ON THE NAVAJO RESERVATION. ProQuest, 10817030. Retrieved from https://search.proquest.com/openview/ab771b94df56ad747c9a64e499803e88/1?pq-origsite=gscholar&cbl=18750&diss=y
- Gluckman, P., 2014, Policy: The art of science advice to government, Nature, 507, 163–165.
- Carrozza, C. (2015). Democratizing Expertise and Environmental Governance: Different Approaches to the Politics of Science and their Relevance for Policy Analysis. Journal of Environmental Policy & Planning, 17(1), 108-126.
- Hulme, Mike (March 14, 2007). "The appliance of science". The Guardian.
- Turnpenny, J., Jones, M., & Lorenzoni, I. (2010). Where now for post-normal science? A critical review of its development, definitions, and uses. Science, Technology & Human Values, 0162243910385789.
- Strand, R., 2017, Post normal Science, The Routledge Handbook of Ecological Economics (Nature and Society) Edited by Clive L. Spash, p. 288-297.
- Gluckman P. (2014) "Policy: The art of science advice to government". Nature, 507, 163-165.
- Grinnell, F. (2015), "Rethink our approach to assessing risk", Nature, 522, 257.
- Nature, Editorial, (2016). "Future present", 531, 7–8.
- Weingart, P. From "Finalization" to "Mode 2": old wine in new bottles?. Social Science Information 36 (4), 1997. Pp. 591-613.
- J. Friedrichs, “Peak energy and climate change: The double bind of post-normal science,” Futures, vol. 43, pp. 469–477, 2011.
- R. A. Pielke, Jr, The Honest Broker. Cambridge University Press, 2007.
- Davies, M.W., Editor, 2011, Special Issue: Postnormal Times Futures, Volume 43, Issue 2, Pages 135-228 (March 2011).
- Andrea Saltelli, Silvio Funtowicz, 2017, What is science’s crisis really about? FUTURES, Volume 91, Pages 5-11.
- Benessia, A., Funtowicz, S., Giampietro, M., Guimarães Pereira, A., Ravetz, J., Saltelli, A., Strand, R., van der Sluijs, J., 2016. The Rightful Place of Science: Science on the Verge. The Consortium for Science, Policy and Outcomes at Arizona State University.
- Ravetz, J., 2016, How should we treat science's growing pains? The Guardian, June 8th 2016.
- Ravetz, J. R. Models as metaphors. in Public participation in sustainability science : a handbook (ed. B. Kasemir, J. Jäger, C. Jaeger, Gardner Matthew T., Clark William C., and W. A.) (Cambridge University Press, 2003).
- Funtowicz, S. O., and Ravetz, J. R. 1990, Post-normal science: A new science for new times, Scientific European, October 1990, p. 20-22.
- Michael A. Peters & Tina Besley (2019): Citizen science and post-normal science in a post-truth era: Democratising knowledge; socialising responsibility, Educational Philosophy and Theory.
- Ravetz, Jerome R. (1979). Scientific knowledge and its social problems. Oxford: Oxford Univ. Press. ISBN 978-0-19-519721-1.
- Ravetz, J. R. (1986). "Usable knowledge, usable ignorance: incomplete science with policy implications." In Clark, W. C., and R. C. Munn, ed. Sustainable development of the biosphere, p. 415–432. New York: Cambridge University Press.
- Funtowicz, S.O. and J.R. Ravetz (1990). Uncertainty and quality in science for policy. Kluwer Academic Publishers, the Netherlands.
- Ravetz, Jerome R. (2005). The No nonsense guide to science. Oxford: New Internationalist.
- Post-Normal Times
- Introductory lecture to Post Normal Science (requires Internet Explorer)
- Article on The Guardian 14 March 2007
- Article on The Conversation (website) September 26, 2016
- More articles on PNS
- About MUSIASEM
- Special issue on Futures
- Centre for Postnormal Policy and Futures Studies, East West University (http://eastwestaffairs.org/cppfs/)