"THE FUNDAMENTALISTS," WROTE Jewish philosopher Abraham Heschel, "claim that all ultimate questions have been answered: the logical positivists maintain that all ultimate questions are meaningless."{1} Professor van Inwagen and I are somewhere in between, concerned about the questions, but not sure of all the answers.
In his paper, Professor van Inwagen presents a kind of systematic doubt grounded in language. He doesn't understand precisely what Darwinism means or what metaphysical naturalism means, or at least he realizes that these terms may have quite different meanings depending on the user. Also, he cannot be sure what a divinely created biosphere would look like in an a priori sense without knowing the purpose for which the biosphere was created. Consequently, it is difficult to draw clear relationships between Darwinism, metaphysical naturalism, and the possibility of a divinely created biosphere.
His focus on the problem of language, on the problem of what particular words mean to the persons who use them, is a key point in any discussion about Darwinism or about science in general. In my response, I want to emphasize and elaborate on this point.
In all social interactions, we communicate with each other according to typical expectations of what sort of language would be appropriate. Some of us who share common interests and activities (for instance, religious or scientific) use language in group-specific ways. When particular words have widely different meanings according to the background and expectations of the speaker and listener, the possibility for confusion increases markedly.
Language confounds our discussion about Darwinism at two levels: the first at the level of communication, the second at the level of imagination. When I read the statement, "Darwinism and neo-Darwinism as generally held and taught in our society carry with them an a priori commitment to metaphysical naturalism," it seems backwards to me. If I wanted to link Darwinism and metaphysical naturalism, I would have written the following. "Metaphysical naturalism is an a priori assumption that makes doing science possible, which includes Darwinism and neo-Darwinism."
As I have described in more detail in my chapter, the assumption of naturalism is necessary for scientists in order to make their research credible. Only by assuming that their research can be verified by others can individual scientists transcend their subjectivity. It is precisely this assumption that grounds the objectivity of science. That is, I assume that my experimental results are not an outcome of my personal biases since I believe that they can be seen and verified, at least potentially, by everyone else. In short, whatever cannot be measured or counted or photographed cannot be science, even if it is important. Therefore, when a writer implies that Darwinism could be separated from an a priori commitment to metaphysical naturalism, I know that he and I understand science to mean different things. We haven't shared the experience of doing science and of trying to make science credible.
The problem of different meanings of the same word can be overcome, at least in part, by trying to make explicit to each other what we mean by the words we use.
The second problem relating to language, that of imagination, is more difficult to overcome. Like other activities of daily life, science depends upon human language for its description. Paradoxically, however, many scientific concepts eventually refer to aspects of reality beyond the possibility of common experience. That is, although science begins with the language of common experience, it often produces descriptions that not only lose their direct connection to, but also may contradict, routine experience. According to quantum physics, tables are mostly empty space, but they feel solid to me. I have trouble imagining an expanding universe. Greek science must have had a tough time convincing people that the earth was spherical rather than flat.
Therefore, despite our attempts at clarity, many scientific ideas are difficult to think about because they cannot be expressed clearly using descriptive language. The situation is like trying to explain to someone who has never seen a red object what the color red looks like. Simply telling the person about the physical events involved in seeing red color-that is, light of a certain wavelength interacts with pigments in the photoreceptors of an observer's eye, etc.-misses entirely the sense of personal experience of redness.
The most obvious differences between science and everyday experience occur in physics, which deals with objects that are very large, very small, and very fast compared to those we normally encounter. Biological thought and language, which is the focus of this conference, present a problem because the objects of biology have histories, histories that count. To describe the evolving characteristics of a group of organisms, one must learn to think in four dimensions, three dimensions of space stretched across a very long dimension of time. The only way I can even begin to imagine what evolutionary thinking might be like is to try to look at my friend as an integrated historical sequence rather than as the individual who confronts me here and now. Not an easy task.
In addition, the uniqueness of such historical sequences impedes usual scientific thinking, which does best when dealing with recurring events. Far from the reductionist ideal, evolutionary biology requires a holistic approach to science. Most people find holistic thinking difftcult. In general, the move away from reductionism has about as much appeal as the uncertainty principle of quantum mechanics had for Albert Einstein. It is not scientists alone, however, who prefer reductionistic descriptions. It took New Testament scholars 1,800 years to begin a hermeneutic approach to biblical interpretation.
In summary, it does not surprise me that Professor van Inwagen has noticed the variable meanings and implications of Darwinism. Like much of science, understanding Darwinism requires us to use our imagination in novel ways that go beyond everyday experience, to use conceptual and mathematic models that can only be approximated by everyday language. That is why we argue about precisely what the models mean. That is why our understanding of Darwinism itself continues to evolve. At any stage, however, what makes different models appear credible in a scientific sense-in the way that I mean science-is their potential for verification, and this verification can occur only in the naturalistic world shared by everyone.