The scientific consensus has been getting a bad rap lately. Some people argue that whether science is right or not about an issue is not decided by majority vote. Rather, it is claimed, it only takes one scientist to be right to decide whether the science regarding an issue is true or not. Those that make this argument then go on to provide a list of scientists that went against the consensus and prevailed. The people making these argument then proudly proclaim that in science there is no such thing as consensus, that science does not require a consensus, and if there is a consensus, then it isn’t science!
Let’s try to understand a few things about the scientific consensus.
A scientific consensus is not reached when scientists get together and “vote”. A scientific consensus, unlike the use of this word in other fields such as politics, does not involve a compromise. Also the word consensus is sometimes used to denote the current state of a field as in “the current consensus”. In a new field of study the term “scientific consensus” really means “the current opinion” and it is understood that such opinion is very likely to be overturned in the future. This is not the meaning of consensus that better serves science in the public sphere when dealing with topics like climate change or evolution. The meaning of scientific consensus that we should seek is that consensus attained in a field of science that is backed by a fully developed scientific theory. A field of science that has not generated a fully developed scientific theory is incapable of generating a true scientific consensus. The reason this is the case is because a fully developed scientific theory has grasped important aspects of reality in its formulation and is likely to have a high degree of completeness.
How is such a theory developed?
When a field of study is in its early stages, scientists from several countries, ethnic backgrounds, beliefs, political persuasions, etc. begin tackling a problem. All these scientists bring their intellect and life experience to bear on answering the questions being investigated. Initially there is a multiplicity of possible answers, there are uncertainties, deficiencies and limitations in the methodologies, and there is confusion. Many scientists go down blind alleys only to find they have wasted their time on a wrong approach and have to turn back. Some explanations emerge that seem to be better than others. Methodologies are improved. Hypotheses are refined. Exceptions are explained. Scientists from other areas enter the field and bring new tools and ideas (a very important development). The research performed in these other fields is found to be complementary to the research in the emerging field. Eventually as the field matures scientists from different laboratories using different methodologies begin obtaining the same results and elaborate models that they use to make predictions (another very important development). Some predictions are not fulfilled and the models that generated them fall by the wayside and are replaced by new models that are more accurate at explaining the data and making new predictions. Eventually the field coalesces around a theory. The theory is used to generate practical applications and to explain observations in other areas of science.
A theory developed through the process described above is not an ephemeral construct that can be overturned at any time. The very technology that we use in our everyday lives depends on hundreds of solid scientific theories that have never been disproven. Many people who do not understand the nature of scientific truth confuse the overturning of a scientific theory with its refinement. This is because there is the erroneous notion that scientific theories should explain everything, and this is not the case. A scientific theory only has to answer the most important questions raised by scientists.
Thus, when a fully developed scientific theory is produced in a field of study this means that scientists have stopped arguing with each other about the salient points addressed by the theory. In other words, they have reached a consensus. This is the true meaning of a scientific consensus. Of course, the fact that there is a consensus doesn’t mean that everything has been settled. Scientists that agree with evolution are still debating how evolution happens. Scientists that agree with climate change are still debating its extent and mechanisms. Nevertheless, a consensus does mean that the major overreaching question in the field has been answered to the satisfaction of the vast majority of the scientists involved in the research.
The consensus can, in principle, be modified if the underlying theory that backs the consensus is found to be incomplete, but this is only true if the refinements to the theory in the form of new observations, new data, or new interpretations of old data or old observations, significantly modify those parts of the theory that are vital for the consensus. In the case of a fully developed scientific theory this is no easy task, and the burden of proof is on those who seek to modify the theory. Some people claim that this promotes a herd mentality that leads to dissenting scientists being penalized and those that are compliant being rewarded resulting in the discouragement of innovation. However, what has to be understood is that science is a very conservative enterprise that sets a very high bar for those seeking to challenge what is considered established knowledge. If you are going against the prevailing theory, you’d better have very good evidence. This is not the product of a herd mentality or a way to discourage innovation: it is a way of protecting established science against error.
In the public debate, when you hear that a consensus has been reached in a particular field of science, you need to ask about the nature of the underlying theory that backs it. If the theory fulfils the requirements of a fully developed scientific theory, then the consensus is good. A consensus is only as good as the theory that supports it. However, suggesting that there is no such thing as a scientific consensus or that it is irrelevant is nothing more than a strategy to delegitimize science. It has been used in the past by entities such as the cigarette lobby, and it is being used today by creationists, climate change deniers, and other groups that seek to further their anti-science agendas.
Image by Nick Youngson used here under an Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) license.