Since the neo-Darwinian synthesis of the 1930s, evolutionary biology has become a growth industry.
This growth has resulted in the demand for more flexible methods of establishing evolutionary biology's grandiose claims than the laborious, difficult, pedantic, and "rigorous" methods favored throughout the rest of the sciences.
This demand has been met by what is now a well-developed branch of evolutionary biology known as evolutionary logic.
I can't here develop the theory of evolutionary logic in detail, but I will introduce some necessary terminology.
In ordinary logic, which is used throughout the rest of the sciences, one is justified asserting that a claim is true provided one can formulate a coherent and rigorous argument that supports it.
In evolutionary logic we relax both these restrictions: an evolutionary claim is true provided there is an evolutionary argument that supports it.
This definition is sufficiently clear as not to require elaboration. Further, we stipulate that any circularity in this definition is virtuous rather than vicious.
The benefits and practical applications of evolutionary logic will be obvious. Professional authors of evolutionary tracts depend on it for their livelihood.
Instructors in evolutionary biology find that evolutionary logic enables them to make complex ideas readily accessible to students regardless of their preparation or background (indeed, proficiency in evolutionary logic has been shown to be positively correlated with high self-esteem).
Research workers in a hurry to claim priority for a new result or who lack the time and inclination to be pedantic find evolutionary logic useful for expeditiously writing up their results.
In this respect evolutionary logic has a further advantage, namely, the results are not required to be true, thus eliminating a tiresome (and now superfluous) restriction on the growth of evolutionary knowledge.
I want next to consider some of the actual techniques for establishing evolutionary claims that evolutionary logic makes available. I will be concerned mainly with ways in which these techniques can be applied in lecture courses -- they require only trivial modification to be used in textbooks, research papers, formal debates, and Internet discussions.
In evolutionary biology, organisms transform by an evolutionary process into other organisms. This means that evolutionary biologists are often called on to establish lineal relationships. There is a whole class of methods that can be applied when an instructor can't quite bridge an evolutionary gap.
Suppose an instructor can get from organism A to organism B and from organism C to organism D by an evolutionary process but cannot bridge the gap between B and C.
A number of techniques are available to the aggressive instructor in this emergency. The instructor can write down B and then, without any hesitation, put "therefore C." If the class is bored or the organisms in question are not terribly interesting, it is unlikely that anyone will question the "therefore."
This is the method of argument by omission and it is remarkably easy to get away with (sorry, "remarkably easy to apply with success").
Alternatively, there is the argument by fiat, where one simply posits an intermediary between B and C -- call it Z -- that shares characteristics of both. The evolutionary transitions from B to Z and then from Z to C are now obvious.
The argument by fiat is a special case of the argument by misdirection, where in place of a difficult problem that was supposed to be solved, one solves an easier problem that is superficially similar to the original problem.
Argument by definition can be extremely effective. Here the instructor defines a set S to be whatever biological systems satisfy some property. For instance, S might consist of all irreducibly complex molecular machines that are the result of Darwinian evolution.
The lecturer then announces that in the future only members of S will be the focus of discussion. Even honors students will take this at face value, not questioning whether the set S might in fact be empty.
Argument by assertion is unanswerable. If, for instance, some vague waffle about an evolutionary transition does not satisfy a recalcitrant student, the instructor simply says, "This point should be intuitively obvious. I've explained it as clearly as I can. If you still cannot see it, you will just have to think very carefully about it yourself, and then you will see how trivial and obvious it is."
The instructor at this point might also want to add, "What are you, a creationist?" or "Are you one of those Christian fundamentalists?" or "Where have you been brainwashed?" Arguments by demonization like this are particularly effective when one or a few students get unruly, but the majority sides with the instructor.
Yet when the majority of the class becomes unruly, nothing beats an argument by obscure reference. This will silence all but the most determined troublemaker. Few students take the time or want to take the time to hunt down an obscure reference in the evolutionary literature.
And even if students locate the reference (which is becoming easier with the Internet), if the reference is sufficiently technical and difficult to understand, it is an easy matter for the instructor to inform the student that he or she simply doesn't comprehend the relevant passage.
In this case, if the instructor is feeling benevolent, he or she may simply offer an argument from removable ignorance -- "Just keep studying evolutionary theory, and eventually it will all make sense." If that doesn't work, the instructor may wish to try an argument from stupidity -- "How can you be so stupid?"
But if the student is otherwise at the top of the class, this approach may backfire. In that case, either the argument from wickedness ("You are just being perverse") or the argument from insanity ("What are you, nuts?") should do the trick. And always keep the argument by demonization in your front pocket.
A variant of the argument by obscure reference is the argument by irrelevant reference. This works in a pinch when you can be reasonably sure that the student won't track down the reference (perhaps because of time constraints). But be careful -- if the irrelevance is palpable (say you are discussing the evolution of vertebrates and the article you cite is on the evolution of organisms in a completely different phylum or even kingdom), then you may be in trouble if the irrelevancy is pointed out.
Make sure the irrelevance is hard to fathom. And then there's the argument by nonexistent reference -- this works best in public debates.
Because the public debate over evolution tends to pit academic high culture against the burger-eating, coke-swilling moronic masses, it is helpful to have a technique specifically for keeping the masses in check and for keeping the academic elite from being seduced by populist sentiments. The argument from aesthetics is the technique of choice here.
"This theory is just too beautiful to be false." Evolutionary biologists regularly use this technique to establish the validity of their theories when the evidence for them otherwise is extremely slender.
By now it will be apparent what riches derive from the study of evolutionary logic. I therefore appeal to evolutionary biologists everywhere to institute formal courses in this discipline. This should preferably be done at the undergraduate level so that those who go to teach with only a bachelor's degree will be familiar with the subject.
But high school students too should be exposed to the rudiments of evolutionary logic. It is certain that in the future no one will be able to claim a biological education without a firm grounding in the practical applications of evolutionary logic.
This article adapts and extends Paul Dunmore's "The Uses of Fallacy," New Zealand Mathematics Magazine, vol. 7, 1970.