Why Darwin Matters_ The Case Against Intelligent Design - Michael Shermer [26]
Either-Or Fallacy, or, disproving A does not prove B.
The either-or fallacy is the false assumption that there are only two positions, A and B, so if A is wrong then B must be right. The fallacy is that discrediting A does not demonstrate B. Both A and B could be wrong and a third alternative could be correct. Creationists employ the either-or fallacy when they claim that life was either divinely created or naturally evolved. By attempting to discredit evolution they hope to draw the conclusion that creationism is true. In science, however, it is not enough to just debunk the accepted theory. You must also replace it with a theory that explains both the “normal” data accounted for by the old theory as well as some of the “anomalous” data not accounted for by the old theory. At the end of my debate with Kent Hovind, for example, he was asked by an audience member: “What is the best evidence for the creation?” He answered: “The impossibility of the contrary” (that is, evolution). In that simple statement, Hovind confessed the scientific sin of creationism and Intelligent Design: Disproving evolution does not prove creationism.
The Fossil Fallacy, or, one datum does not a science make.
In debates with creationists they often demand “just one transitional fossil” that proves evolution, pointing to a gap in the fossil record. When I fill the gap—for example, with Ambulocetus natans, a transitional fossil between ancient land mammals and modern whales—they respond that there are now two gaps in the fossil record! This is a clever retort, but it reveals a deep error in epistemology that I call the Fossil Fallacy: the belief that a single “fossil”—one bit of data—constitutes proof of a multifarious process or historical sequence.5
Proof is derived not through a single piece of evidence, but through that convergence of evidence from numerous lines of inquiry, all of which point to an unmistakable conclusion. We know evolution happened not because of a single transitional fossil such as Ambulocetus natans, but because of the convergence of evidence from such diverse fields as geology, paleontology, biogeography, comparative anatomy and physiology, molecular biology, genetics, and many more. Paleontologist Donald Prothero, for example, employs the convergence technique in revealing that in addition to at least eight transitional fossils from land mammals to whales, DNA from living specimens reveals that modern whales descended from even-toed hoofed mammals called artiodactyls. Whales, it turns out, are most closely related to the hippopotamus.6
No single discovery from any one field constitutes proof of evolution. It is the mass of data together, converging to reveal that life evolved in a specific sequence by a particular process, that makes the theory of evolution a singular landmark in our understanding of the world.
Methodological Naturalism, or, no miracles allowed.
In one of Sidney Harris’s most poignant cartoons, two scientists are at a blackboard filled with equations, in which the words “THEN A MIRACLE OCCURS” appear in the middle. The caption has one scientist saying to the other: “I THINK YOU NEED TO BE MORE EXPLICIT HERE IN STEP TWO.” This is what we call the God of the Gaps argument—wherever an apparent gap exists in scientific knowledge, this is where God interjects a miracle. Intelligent Design advocates argue something like this:
• X looks designed
• I can’t think of how X could have been designed naturally
• Therefore X must have been designed supernaturally
This is comparable to the “plane problem” of Isaac Newton’s time: The planets all lie in a plane (the plane of the ecliptic) and revolve about the sun in the same direction. Newton found this arrangement to be so improbable that he invoked God as an explanation at the end of his magisterial work Principia Mathematica: “This most beautiful system of the sun, planets, and comets could only proceed from the counsel