Logical Fallacy of Extended Analogy

Extended analogy is one of the many smokescreens that are used to cover the fact that the reasoning is based on one of the three fallacies of Agrippa's trilemma. Whenever a logical fallacy is committed, the fallacy has its roots in Agrippa's trilemma. All human thought (without Divine revelation) is based on one of three unhappy possibilities. These three possibilities are infinite regress, circular reasoning, or axiomatic thinking. This problem is known as Agrippa's trilemma. Some have claimed that only logic and math can be known without Divine revelation; however, that is not true. There is no reason to trust either logic or math without Divine revelation. Science is also limited to the pragmatic because of the weakness on human reasoning, which is known as Agrippa's trilemma.

The logical fallacy of extended analogy occurs when two things that are similar to a third thing are said to be like each other without further proof of that fact.

Examples of the Logical Fallacy of Extended Analogy

"Macro-evolution is a scientific theory. Gravity is a scientific theory. Therefore, to deny macro-evolution is to deny the Law of Gravity."

Or

"Macro-evolution is a scientific theory. Gravity is a scientific theory. Therefore macro-evolution is as solidly known as the Law of Gravity."

Statements like these play on the ignorance of those listening to them. Note that macro-evolution has never been observed even in the fossil record. We see variation within kinds of living things to the edges of the families of living things but nothing in between. The tree of life is actually a forest of individual trees that are separated right about the level of families. However, gravity is observed. The various competing theories of gravity have not been observed, but there is a Law of Gravity, and the Law simply describes what we observe about gravity. There is no law of macro-evolution because there is nothing that can be observed.

"Radiometry dating is observed in the present. The application of radiometric dating methods is observed in the present. Therefore, the science of radiometric dating methods is as solid as radiometry."

Actually, though radiometry is used as one of the processes for radiometric dating, the two are not at all on the same footing scientifically.

Fallacy Abuse

Roxanne: "Science is a process that gets things wrong. For example, scientists once were very sure that the Sun went around the Earth. There are other examples. The things you are so sure are settled science, evolution, billions of years, non-existence of the global flood, and other “settled science” that conflicts with Scripture, is not settled science at all."

Sandy: "Ha Ha! To see your fallacy, let’s put this in the logical form. Major Premise: Being certain that the Sun goes around the Earth was a mistake of science. Minor Premise: Being certain of present theories that conflict with the Bible is a mistake of science. Conclusion: Therefore, virtually all scientists being certain that the Sun goes around the Earth is like being certain of present theories that conflict with the Bible. That is the fallacy of extended analogy. Why don’t you learn something about logic before talking???!!!"

Roxanne: "That’s a straw man argument since that is not the conclusion that I came to. In logical for, it would go this way. Major Premise: All scientific theories are tentative and subject to change based on new discoveries. Minor Premise: Present theories that conflict with Scripture belong to the class: ‘all scientific theories.’ Conclusion: Therefore, present theories that conflict with Scripture are tentative and subject to change based on new discoveries."

Note how Sandy superficially applied the form of the logical fallacy onto Roxanne’s words, converting a simple example, that was brought in on the side merely to facilitate understanding, into the major premise. The cleverness of this ploy cannot be denied, but such tactics aren’t used by anyone interested in truth.