In the history of modern western thought, evolutionary thinking arose as a consequence of several theological and philosophical traditions mandating purely naturalistic explanations in the historical sciences. One of these traditions was the perceived intellectual necessity of naturalism. Without naturalistic explanations, it has been argued since the nineteenth century, science is impossible. That's right, impossible.

The argument given with increasing conviction was not that naturalistic explanations were superior in certain regards, or in certain applications, but that they were absolutely necessary for science. Nor was this conviction a consequence of successful, empirically based science. The argument arose from metaphysical concerns about God and creation. This explains the certainty with which thinkers adopted naturalism. Metaphysics leads to truth claims far more readily than the empirical sciences.

Naturalistic explanations were mandated for the sake of science and the advancement of our knowledge. As the nineteenth century Reverend and professor Baden Powell put it, "to deny [the continuity of natural laws] in any instance would be to endanger all science."

This is an example of how rationalism has influenced modern science. A great many empiricists have argued that science should follow the data, wherever it may lead. But there has been a constant rationalistic pressure on science, calling for restrictions on science's methods and results.

Venture outside those restrictions, the rationalist warns, and you've ventured outside of science. Defining the demarcation between science and non science is a challenge for those who study the problem, but not so for many rationalists. They have their metaphysical criteria with which to draw the line. As A. F. Chalmers explained:

The distinction between science and non-science is straight-forward for the rationalist. Only those theories that are such that they can be clearly assessed in terms of the universal criterion and which survive the test are scientific. [1]

In my talk I had a chance to develop this background, and the ensuing discussion provided a live demonstration. I began the discussion with half-a-dozen scientific challenges to evolution. These were not details, but rather concerns regarding the core of evolution. Any empiricists in the audience would have been disappointed though, as the evidences were dismissed with a wave of the hand. Not a problem.

Most of the scientific examples I presented were ignored and a perfunctory reading of the usual ambiguous evidences was given (breeding and adaptation, biogeography, the fossil record, extinctions, vestigial structures, suboptimal designs, age of the Earth, etc.). The focus of the evolutionist's discussion was on demarcation arguments against intelligent design. It was rationalism on steroids as the evolutionists defended their theory not on the basis of the scientific evidence, but because the alternatives must be disallowed. Who needs evidence? If design theory is out of bounds then of course let's stick with evolution. It was right out of the history of thought I had described.

I marveled at how well the evolutionists followed my script. I had explained in no uncertain terms that evolution is rationalistic and motivated by metaphysical and philosophical concerns, in spite of the empirical evidence. And I pointed out how this led to, among other things, evolutionists relying on demarcation claims to justify their theory. Evolution is the only acceptable option, for the alternatives are unacceptable. I had described this tradition in the history of evolutionary thinking, and now the evolutionists provided a real-time demonstration.

It is one thing to predict human behavior in secret, but quite another thing to explain to someone's face how they are going to argue. One might have thought that the evolutionists, just to spite me, would have at least attempted to engage the scientific issues I raised rather than plunging into the philosophical tributaries I had claimed to be at the core of evolutionary thinking.

Indeed, their claim was that my empirical challenges were trivial. So why not go there? Why protect evolution with obvious philosophical arguments when you have the empirical goods? Why not explain why the scientific quandaries that have people wondering about evolution are all about nothing? I would have been the first to sign up.

Of course the answer is obvious. There indeed are serious scientific challenges to evolution that are awkward to face. There have always been such challenges. Evolutionary thinking is, and always has been, motivated by philosophical and theological concerns rather than the empirical evidence.

[1] A. F. Chalmers, What is this thing called science? 2d ed, (Indianapolis, IN.: Hackett Publishing Company, 1982) 102.