Evolution III: Scientific knowledge is an interconnected web

(I will be traveling for the next few weeks and rather than put this blog on hiatus, thought that I would continue with my weekday posting schedule by reposting some of the very early items, for those who might have missed them the first time around.)

In an <a href=http://blog.case.edu/mxs24/2005/02/09/evolution_ii_science_is_not_a_smorgasbordearlier posting, the question was posed as to whether it was intellectually consistent to reject the findings of an entire modern scientific discipline (like biology) or of a major theoretical structure (like the theory of evolution) while accepting all the other theories of science.

The short answer is no. Why this is so can be seen by examining closely the most minimal of creationist theories, the one that goes under the label of ‘intelligent design’ or ID.

ID supporters take great pains to claim that theirs is a scientific theory that has nothing to do with religion or God, and hence belongs in the school science curriculum. (This particular question whether ID can be considered a part of science or of religion will be revisited in a later posting. This is becoming a longer series than I anticipated…)

ID advocates say that there are five specific biochemical systems and processes (bacterial flagella and cilia, blood clotting, protein transport within a cell, the immune system, and metabolic pathways) whose existence and/or workings cannot be explained by evolutionary theory and that hence one has to postulate that such phenomena are evidence of design and of the existence of a designer.

The substance of their arguments is: “You can claim all the other results for evolutionary theory. What would be the harm in allowing these five small systems to have an alternative explanation?”

Leaving aside the many other arguments that can be raised against this position (including those from biologists that these five systems are hardly intractable problems for evolutionary theory), I want to focus on just one feature of the argument. Is it possible to accept that just these five processes were created by a ‘designer,’ while retaining a belief in all the other theories of science?

No you cannot. If some undetectable agent had intervened to create the cilia (say), then in that single act at a microscopic level, you have violated fundamental laws of physics such as the law of conservation of energy, the law of conservation of momentum, and (possibly) the law of conservation of angular momentum. These laws are the bedrock of science and to abandon them is to abandon some of the most fundamental elements of modern science.

So rejecting a seemingly small element of evolutionary theory triggers a catastrophe in a seemingly far-removed area of science, a kind of chaotic ‘butterfly effect’ for scientific theories.

Scientific theories are so interconnected that some philosophers of science have taken this to the extreme (as philosophers are wont to do) and argued that we can only think of one big scientific theory that encompasses everything. It is this entire system (and not any single part of it) that should be compared with nature.

Pierre Duhem in his The Aim and Structure of Physical Theory (1906) articulated this position when he declared that: “The only experimental check on a physical theory which is not illogical consists in comparing the entire system of the physical theory with the whole group of experimental laws, and in judging whether the latter is represented by the former in a satisfactory manner.” (emphasis in original)

Of course, in practical terms, we don’t do that. Each scientific subfield proceeds along its own path. And we know that there have been revolutions in one area of science that have left other areas seemingly undisturbed. But this interconnectedness is a reality and explains why scientific theories are so resistant to change. Scientists realize that changing one portion requires, at the very least, making some accommodations in theories that are connected to it, and it is this process of adjustments that takes time and effort and prevents trivial events from triggering changes.

This is why it usually requires a major crisis in an existing theory for scientists to even consider replacing it with a new one. The five cases raised by ID advocates do not come close to creating that kind of crisis. They are like flies in the path of a lumbering evolutionary theory elephant, minor irritants that can be ignored or swatted away easily.

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