2:This argument is invalid because it uses different meanings of the word theory. Its illogical result arises from changing the meaning of the word theory between premise 1 (“a well-substantiated scientific truth”) and premise 2 (“a guess”). This has also been called the four-term fallacy because of the two different meanings of theory. The correct syllogism is:
| Premise 1: | Evolution is a theory. | |
| Premise 2: | A theory is a well-supported explanation of many observations. | |
| Conclusion: | Therefore, evolution is a well-supported explanation of many observations. |
This form of the argument is valid and the premises are true, so the conclusion is true. It is puzzling that creationists continue to assert that evolution is “only a guess.”
A third instructive example of the equivocation fallacy is the following:
| Premise 1: | Humans are a species. | |
| Premise 2: | A species is a mental construct. | |
| Conclusion: | Humans are a mental construct. |
The concept of a species is a mental construct, a creation of the human mind, but that is different from human beings being a species. To make a valid argument, the statements should be as follows:
| Premise 1: | Humans are interfertile with other humans. (That is, they can interbreed.) | |
| Premise 2: | A group of interfertile individuals is termed a species. | |
| Conclusion: | Humans are a group called a species. |
3. The excluded-middle fallacy: assuming that only two alternative explanations exist, black or white. (E.g.: if Darwinism is false, then Genesis must be true.) There is no allowance for a gray or intermediate theory. This is a very important fallacy in the discussion between scientists and creationists. Creationists often construct a world with only two arguable views: creationism, and materialism/naturalism. There is no recognition that more than one version of creationism exists, such as “young-Earth” versus “old-Earth” creationists. Similarly, there is no recognition that more than one version of naturalism exists, such as Lamarckism and Darwinian evolution. This produces a situation in which there are, seemingly, only two contending theories, one of which then must be false and the other must be true. Such circumstances are wonderful but rarely occur in nature, because by proving that one of the contenders is wrong (the evolutionist position), one appears to prove that the other contender is necessarily right (the creationist position). Unfortunately, this argument has a major logical flaw. That flaw is that one is not allowed, arbitrarily, to omit some explanations, or to tie several of them together to get a single entity, in order to reduce the logical system down to a maximum of only two components.
For example, how can the synthesizing machinery obtain the correct sequence of amino acids in a protein? The creationists have their choice: model 1 (God does it); and model 2, a random model for which they can calculate probabilities. Model 2 is the creationist view of what they think evolutionists believe. The creationists make the calculations and rightly reject these random models. Having rejected model 2, they then infer that the creationist model, model 1, must be right. But the inference requires that there be no third model, random or not. In fact there are an infinite number of possible different models. The conclusion depends upon there being no other random models, including a model 3, which is discussed later on (see chapter 3, section B). More than two possible models are conceivable. Thus the creationist argument is already a failure because it is limited to only two possible models. But it gets worse. The evolutionist argument for model 3 has a very high probability of forming the whole protein without error.
4. The genetic fallacy: arguing against an idea on the basis of the proponent's personal character. An example is: “That man is a natural born idiot. How could any self-respecting human vote for his proposal.?” [See ad hominem]
5. The naturalistic fallacy: asserting what ought to be true on the basis of what appears to be true. A disquieting example of this fallacy: Some animals eat their young; therefore it would be OK if humans were to eat theirs. This can be stated as a syllogism as follows:
| Premise 1: | It is acceptable for humans to do what some animals do. | |
| Premise 2: | Some animals eat their young. | |
| Conclusion: | Therefore, it is acceptable for humans to eat their young. |
Premise 1 is disquieting but not necessarily in itself false. Premise 2 is true. The conclusion appears to be true, so the argument is valid. But the argument is not morally acceptable. In the early nineteenth century, the social Darwinists (see the discussion in chapter 2, section B) accepted all this and tried to sterilize mentally disabled people and deny them schooling and welfare etc. on the grounds that the intended recipients were inferior, by nature, and so could not benefit from education. Logic fails us here, but only because ethics and morality are not considered. Logical deductive reasoning can tell us when certain facts are true in terms of a “truth table,” but it does not prescribe how those facts should be used. The conclusions drawn from a logical, abstract evaluation may be unacceptable in moral terms or irrelevant to our daily lives (e.g., an imaginary situation). The term naturalistic fallacy was originally defined (by G. E. Moore) somewhat differently from how the current popular definition describes it. The naturalistic fallacy is summarized more frequently by saying that we must not assume an “ought” from an “is.” As Albert Einstein wrote, “For the scientific method can teach us nothing beyond how facts are related to, and conditioned by each other…. knowledge of what is does not open the door directly to what should be” (1954, pp. 41—49).
The Italian cardinal Caesar Baronius (quoted by Galileo in his letters) summed up the separation of ethical philosophy from scientific study in i598 with a wise remark; “The Bible was written to tell us how to go to heaven, not how the heavens go.” In the Bible (Luke 20:24—25), a commission of hostile priests challenges Jesus on the issue of authority, asking him whether it is lawful for a believer to pay taxes to a secular authority such as Caesar. Jesus's response is:
“Shew me a penny. Whose image and superscription hath it?” They answered and said, “Caesar's.” And he said unto them, “Render therefore unto Caesar the things which are Caesar's, and unto God the things which be God's.”
We could do worse than to consider ethics and morality to be God's domain, and natural science to be Caesar's.
6. The non sequitur (Latin for “does not follow”) fallacy: asserting that a conclusion follows from the preceding material when it in fact does not. For example: “That critical reviewers advance scientific arguments against intelligent design (whether successfully or not) shows that intelligent design is indeed falsifiable” (Behe 2000). To see the incorrectness of the argument, replace the words intelligent design in the syllogism below with the word God, which leads to the conclusion that God is falsifiable. All fallacies are, in one way or another, non sequiturs.
The argument, expressed as a syllogism, is as follows:
| Premise 1: | Intelligent design has been argued against by scientists. | |
| Premise 2: | If scientists can argue against (or for) intelligent design, it is falsifiable. | |
| Conclusion: | Therefore, intelligent design is falsifiable. |
To be considered scientific, a theory must be falsifiable—that is, you should be able to prove the theory false if a particul ar fact is observed; otherwise, you have no means of testing the theory by experiment. In the syllogism above, the argument is valid in that the conclusion
