Can you feel the fever of the divisive tide? The Great Flood is here. The water is wide between those who say Intelligent Design Creationism has no place in science class and those who dismiss evolution as “just a theory.” Of course there is a flaw at the root of such controversy. Of course faith and science are not mutually exclusive. So the water is not deep. To hyper-extend a metaphor, you could stand up and wade to shore without getting your knees wet. But we’re past that already, up to our f**king ears in semantics.

I hear the phrase “just a theory” on the news and see it in print so often now that it gives me blisters. For instance, the New York times reported on creation versus geology explanations of patterns in the rock of the Grand Canyon (“Seeing Creation and Evolution in the Grand Canyon” 10/6/2005). In the article, a creationist guide is explaining that a fold in the rock, like everything you see in the canyon, was caused by the Great Flood.

"You see any cracks in that?" he asked. "Instead of bending like that, it should have cracked." The material "had to be soft" to bend, Mr. Vail said, imagining its formation in the flood. When somebody suggested that pressure over time could create plasticity in the rocks, Mr. Vail said, "That's just a theory."

A theory, indeed. What is a theory? Is it the kind of thing one should generally condition with a word like “just?” The tiniest goal in the Intelligent Design Creationism movement is to have teachers emphasize that evolution is a theory. Perhaps the attainment of this tiny goal will be a crack in the dam, a stepping stone to using textbooks designed “intelligently” to go a bit further and renounce science altogether, or perhaps it will end up engaging America’s youth in science as a skeptical process rather than a body of Truth. I would favor the second agenda, because I know what a theory is.

There are two kinds of theory: top-down and bottom-up. Bottom-up theories are somewhat rare. They arise when disparate forms of evidence congeal into a single body of knowledge without the need for much more testing. Top-down theories are proposed by synthetic thinkers and include conceptual links that have not yet been tested empirically. Top-down theories drive the direction of a scientific field by presenting a set of testable hypotheses. No top-down theory will last long unless it can accommodate change in its logical structure, because a top-down theory is rarely completely accurate when first proposed.

In the structure and hierarchy of knowledge, there are Laws, Theories, Hypotheses, Concepts, and Observations. Among the Laws, there are Manufactured Laws, such as those governing our behavior in traffic. But the truly magnificent ones are the Observed Laws. These Laws of Nature are so powerful that they become part of the fabric of both secular and sacred sides of a debate. The classic example:

“Evolution contradicts Newton’s Second Law of Thermodynamics, which states that systems should lose organization over time. The evolution of forms of increasing complexity implies a process that somehow defeats entropy.”

“The Second Law applies at the scale of closed systems. Earth is an open system and receives energy from the sun. The sun is decaying, so there’s your entropy. Moreover, evolution does not necessarily lead to an increase in complexity. For instance, we can observe the evolution of smaller genomes in viruses and bacteria.”

To have an Observed Law for something means there were first facts (observed), then curiosity leading to formal questions and putative answers (hypotheses), then tests, falsification, and revision of those hypotheses (experimentation or structured observation). The process is like a slow Socratic dialogue in which every argument is examined critically as a network of ideas is built to describe how the world works, including rules and mechanisms for exceptions. This network, incorporating the knowledge gained from the rejection of (or the failure to reject) many hypotheses, is a theory. If the theory is very simple, if it is elegant, if it is general, if all its parts are tested and bolstered and buttressed by observations, then it is a Law. Otherwise, it is just a theory.

Just a theory? Meaning what? It isn’t good enough to be a Law? Well, yes. But why? Some theories are simply not simple enough. They contend with too many exceptions. In ecology, the theory of population dynamics is a very good example. The theory says that populations grow or decline according to birth and death rates. Fine, but they also cycle and for various reasons. And are they limited or regulated? Some are this, some are that. The theory of population dynamics is a work in progress. It is neither simple, nor general, nor elegant. It’s just not a law. BUT, it is nonetheless a body of knowledge, a good chunk of gelatin, comprising facts and concepts. The concepts are empirically testable, revisable, and rejectable.

Why isn’t the theory of evolution a Law? Why is it “just a theory?” Evolution is not yet a Law for two simple reasons: 1) holes in the fossil record and 2) monkeys didn’t just fly out of my butt. Regarding the holes in the fossil record, it is true that the lack of intermediate forms leaves scientists wondering at the tempo and mode of evolution. Is it gradual or saltatory? Do complex organs arise all at once or in steps? Understand that there is evidence to support both answers to both of these questions. More evidence is required before we know exactly how evolution has worked in the past. Regarding the monkeys that didn’t fly out of my butt, that’s because monkeys are both flightless and too large to pass through my anus. I get the idea that if people could “watch” monkeys shrink to the size of, say, a gerbil and “sprout” wings, then everyone would “believe in” evolution. They wouldn’t understand, but they would believe.

Truly, evolution is a theory because it is supported by so many observations and because it makes testable predictions about the diversification of life on Earth. It is a work in progress because major evolutionary events (other than extinctions) happen slowly and are not always recorded in the fossil record. For these reasons, there is not yet consensus on how life began or on whether our decendents will attain a third pair of limbs. However, to have become a theory and withstood scientific scrutiny for 150 hundred years means there is no doubt that evolution does occur. Darwin’s publications were a step in the process of forming and testing a theory. His life’s work was much like evolution itself, differing a little from that of his predecessors and successors. His hypotheses were based upon observations, and were upheld, revised, or overturned by further observation. Turned and turned, the way a river smoothes a stone.

Here’s what we know about evolution now:

• Traits are passed from parents to offspring as information contained in DNA.
• Some traits expressed in the offspring result from other constituents of the parental gametes or cells, such as energy stores or pre-transcribed RNA. These are often called maternal effects.
• Heritable mutations occur at what strikes me as a pretty high rate, meaning that children and grandchildren will differ from their parents.
• Some of the more dramatic changes in body plan result not from mutations in genes for particular traits but in changes in the regulatory pathways that govern development. Mutations, deletions, inversions, and duplications can bring about rapid morphological change in a lineage. We have observed it happen in all the major genetic models: viruses, bacteria, yeast, nematodes, fruit flies, and mice. Evolution happens, is an inevitable consequence given the slight inaccuracy of earthly life’s means of inheritance (That part is just about Law).
• We know that adaptation can occur in response to persistent directional selection or to persistent uncertainty about the direction of selection.
• We know that speciation happens and we know that it can happen either for adaptive reasons or simply out of a chance loss of mating compatibility.
• We have a good idea of the age of the earth (4.5 b.y.).
• We know that evolution in some species has begotten evolution in other species, both deep in the earth’s past and last year.
• We know that innovations in life have changed the planet and continue to do so.
• We have a good idea of when life began (~3.5 bya) and we think that all forms of life on Earth today share a common ancestor, though there is some room for argument that the various branches of bacteria had separate origins and later homogenized by the horizontal transfer of DNA.
• We even suspect that life began more than once, perhaps succeeding only on the third try. We suspect, but we do not know. That part’s just a theory.

Theories are part of the democratic process of knowledge-building. They must be malleable rather than absolute. Inevitably, theories contain paradoxes, which are like steroids for a scientist’s imagination. If a paradox cannot be resolved, the theory is weakened by attack from specialists until it is torn asunder and built anew. Darwin’s ideas almost vanished from scientific thinking in the early 20th century for lack of a mechanism of inheritance. The revitalization of evolutionary thought following the identification of DNA as the vehicle of the genetic code is an unparalleled example of what it means to be a theory. No support, no theory. To say, then, that evolution is a theory is to announce to a classroom of America’s youth that they, too, have the power to shape our understanding of the world by careful observation and logical argument.

I will conclude this rant with a note on what might disqualify an idea from being a theory. If the mechanism proposed to explain and relate observations is not testable, then the idea is a theory only in the semantically-confusing sense of “operational construct.” The theory of "chi," the proposition that there is a common energy of life flowing through all things which can be channeled by meditation, is an operational construct. It is a nice idea, and we might benefit psychologically by viewing the world through its lens, but we have no test to accept or reject it. Not really a theory. Intelligent Design Creationism is another idea that is not a theory. The doctrine’s sole empirical basis is the observation that living things sure are complicated, gosh. Its sole tenet is framed not in terms of logic, philosophy, or mathematics, but in terms of Timex and Seiko. “When I see a watch, I never question that such a complex thing was made by an intentional being.” The sole mechanism it proposes is a Maker, presumably one with Intelligence (hence: People Magazine, feaux-hawks, malaria, lemmings, and George W. Bush). What shall we test to support or reject the doctrine of Intelligent Design Creationism? There is not one testable hypothesis, not one prediction, only the nagging Cartesian utterance, “I can imagine an undeceiving God, so He must exist.” Like chi, Intelligent Design Creationism would be a great topic in a class called Modern Mysteries – spirituality in an age of reason. Science class, on the other hand, should be just theories.