Science Fair Project Encyclopedia
Scientific consensus is the significant majority agreement of scientists in a particular field of science at a particular time.
In most scientific fields there is no specific mechanism, perceptible to those outside the field, to achieve consensus or to recognize it when it has been achieved. Nonetheless conferences, the process of publication and peer review lead to a situation where those within the discipline can recognize such a consensus where it exists. Scientists in a specific field reach a consensus through a process of experimentation, through the application of the scientific method, and through peer review and publication. In cases where there is little doubt regarding the subject under study, establishing what the consensus is can be quite straightforward. In cases where there is still significant doubt among that scientific community, methods such as polling are sometimes used to ascertain the existing scientific consensus.
The issue of consensus is important in the philosophy of science. The view that the goal of science is the creation of such a consensus holds that the scientist is a skeptic using his or her analytical and critical faculties to evaluate all evidence presented before delivering an opinion. Unlike other forms of knowledge, scientific knowledge consists of messages that are consensible - that is they can be mutually understood so that they can be evaluated for agreement or dissent and have the possibility of becoming part of the consensus. Thus, consensibility is a prerequisite for consensuality. 
Lack of substantial doubt
In its strongest form, the term is used to assert that on a given question scientists within a particular field of science have reached an agreement of rational opinion without substantial doubt, through a process of experimentation and peer review (see scientific method).
For example, in physics there exists scientific consensus on general relativity and quantum mechanics. Special relativity and quantum mechanics are unified in the framework of quantum field theory (QFT). There exists scientific consensus that QFT is a very useful description, but it is not a final theory. For example, it does not include gravity. General relativity, and quantum mechanics may be unified by superstring theory but there is no consensus whether this candidate unifying theory is the correct description of reality.
Uncertainty and scientific consensus in policy making
In public policy debates, the assertion that there exists a consensus of scientists in a particular field is often used as an argument for the validity of a theory and as support for a course of action.
Science is by its nature uncertain. Absolute certainty is alien to science. Scientists work incessantly in two directions: first they seek verification, designing experiments to test theories with the goal of either verifying and adding a degree of confidence or support for the current theory, thereby increasing its confidence level. Or conversely, with the goal of disproving or finding contradictory evidence which may either negate or strongly modify the theory in question. With each positive test the theory gains confidence, but it is never absolutely proven.
This inherent uncertainty poses a problem for politicians, policy makers, lawyers, and business professionals. Decisions must be made now even though the scientific basis for those decisions is uncertain. Therefore, the various policy makers must rely on a consensus of scientific opinion as to what course of action to take. A scientific consensus must be achieved to justify required action in face of uncertainty. Whether it is a mining company seeking consensus from its geologists and engineers before taking a risk on a mining venture; or a political leader seeking consensus from his technical and science advisors on the risks of a controversial progam or military deployment; or a multi-government body seeking consensus from a wide variety of scientists before taking action on a global environmental problem: decisions must be made without complete certainty.
As an example of politicians working with scientists and reporting the scientific consensus: the reports of the United Nations' Intergovernmental Panel on Climate Change (IPCC) are considered to amount to a scientific consensus on the various issues of climate change and the global environmental and economic challenges to be addressed. The Kyoto Protocol is an action based in part on this scientific consensus.
Because decisions must always be made in the absence of complete certainty, scientific consensus is relied upon to aid in the decision process. It has been noted that the scientists involved in consensus forming may be affected by political pressures on them and by their own political views, such that they emphasize the achievement of consensus with a desired result in itself over conducting thorough, unbiased science. This distortion of scientific consensus toward ideological or political ends has been criticized and referred to as consensus science.
How consensus can change over time
While consensus exists in a wide range of scientific fields, objectors can usually be found for all of these. Consensus usually means overwhelming majority, not simple majority nor total agreement.
One mark of the consensus is that it is the theory against which all challengers must be compared. It is also the paradigm to be challenged and tested by new experiments.
In the case of relativity and quantum mechanics, the expectation is that these theories will be replaced by a Grand Unification Theory. There are candidates, but there is certainly no consensus on a suitable candidate as a unifying theory. Nor does consensus mean that the theory is fully understood - there remain problems with the interpretation of the meaning of quantum mechanics, for examples, even though its predictions are precise.
Formerly, there was a consensus that Newtonian gravity was correct, in part because its predictions were extremely good. Over time, various objections to the theory mounted. One in particular was the precession of the perihelion of the orbit of Mercury. However, despite increasingly clear observations of an anomaly, and the failure of various attempts to explain it away, the failure to of the theory to match observations was not considered the death knell of the theory. Today, the scientific consensus is that the Newtonian gravity is just a very useful approximation of general relativity which itself may be superseded by a more complete theory sometime in the future.
Scientific consensus and the scientific minority
In a standard application of the psychological principle of confirmation bias, scientific research which supports the existing scientific consensus is usually more favorably received than research which contradicts the existing consensus. In some cases, those who question the current paradigm are at times heavily criticized for their assessments. Research which questions a well supported scientific theory is usually more closely scrutinized in order to assess whether it is well researched and carefully documented. This caution and careful scrutiny is used to ensure that science is protected from a premature divergence away from ideas supported by extensive research and toward new ideas which have yet to stand the testing by extensive research. However, this often results in conflict between the supporters of new ideas and supporters of more dominant ideas, both in cases where the new idea is later accepted and in cases where it is later abandoned. Thomas Kuhn in his 1962 book The Structure of Scientific Revolutions discussed this problem in detail.
Several examples of this are present in the relatively recent history of science. For example:
- the theory of continental drift proposed by Alfred Wegener and supported by Alexander Du Toit and Arthur Holmes but soundly rejected by most geologists until indisputable evidence was presented after 50 years of rejection.
- the theory of symbiogenesis presented by Lynn Margulis and initially rejected by biologists but now generally accepted.
- the theory of punctuated equilibria proposed by Stephen Gould and Niles Eldredge which is still debated but becoming more accepted in evolutionary theory.
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