Axis Mundi:

The Tree at the Center of the World

On "Scientific Consensus"
On "Scientific Consensus"

There is a great deal of interdependence between scientific disciplines - I have pointed out as much in relation to Duhem's thesis previously. Typically, if someone is to test a given advanced theory, there will be a great number of other, earlier scientific conclusions which one will have to presuppose are true, even though it is at least "possible in principle" that evidence at some point may be discovered which would require that individual to abandon one of those background assumptions.

The test of a hypothesis M will generally be of the form if A&B&C&...&M then e, and M is regarded as failing the test if not e. But if any of the background assumptions were in fact false, then M might be true with not e or false with e, and the test would be an invalid test of M for either the purpose of confirmation or disconfirmation. Or to put it another way, in principle at least, the test is a test not of M but always of A&...M.

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Likewise, the more broadly integrative theories will rely upon the conclusions in a wide variety of disciplines, implications in a wide variety of of disciplines and have explanatory power in a wide variety of disciplines. At the same time, modern science requires a large division of cognitive labor. It is divided into fields, disciplines, sub-disciplines and sub-sub-disciplines. Few people can achieve any real expertise in more than a handful or so areas.

As such, while someone may be able to state as a matter of their own expertise that a given theory or (narrower) theoretical principle which cuts across a wide variety of disciplines is well-supported by the evidence in their field as a matter of their own expertise, they will generally be unable to do so in a variety of other fields where that theory or principle applies. Likewise, they will generally tend be unaware of many of the issues which had previously decided in favor of the principles which their discipline takes for granted - except at a fairly cursory level.

As such, experts throughout the scientific endeavor generally have to rely upon points that are at least tacitly dependent upon a form of scientific consensus -- whether they are aware of this or not. Its unavoidable.

But at the same time, it generally isn't something which they have to be all that aware of - precisely because the principles which have become part of the well-established consensus are well-established. We generally become self-consciously aware of expert consensus and the need for it only at the interface between the scientific community and the broader community in which it is embedded.

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There have been points at which the very notion of a "scientific consensus" has come under attack, and no doubt there will be in the future. Typically, such attacks will rely upon an equivocation between appealing to a scientific consensus and "appeal to the majority," or alternatively, assume that an appeal to the scientific consensus is an appeal that is independent of the actual evidence upon which a decision should be based.

However, the scientific consensus is a consensus of experts, each acting as an expert alongside other experts in his or her own field. These experts are gathering evidence, generating theories, forming hypotheses, making predictions - and testing theories - and their views become relevant to and incorporated into the consensus on a given issue only to the extent that their area of expertise is relevant to that conclusion. As such, the scientific consensus is evidence-based.

It is not simply a form of an "appeal to the majority." It is, in essence, an appeal to a congress of individuals who are acknowledged and tested experts in their respective fields - where the weight given to any voice is a matter of the relevance of the expertise.

Given the collective extent of those fields, this exposes the conclusions to a far larger body of evidence and tests than would be possible by means of any one field considered in isolation from the rest. Consequently, the justification for a conclusion arrived at by means of the congress can be far greater than that which the conclusion would receive if it were simply supported by only one or a handful of disciplines.