False analogy

From Wikipedia, the free encyclopedia

False analogy is a fallacy applying to inductive arguments. It is often mistakenly considered to be a logical fallacy, but it is not, because a false analogy consists of an error in the substance of an argument (the content of the analogy itself), not an error in the logical structure of the argument. Thus, it is an informal fallacy, not a formal logical fallacy.

In an analogy, two concepts, objects, or events proposed to be similar in nature (A and B) are shown to have some common relationship with another property. The premise is that A has property X, and thus B must also have property X (due to the assumed similarity of A and B). In false analogies, though A and B may be similar in one respect (such as color) they may not both share property X (e.g. size). Thus, even if bananas and the sun appear yellow, one could not conclude that they are the same size. Many languages have culturally idiosyncratic idioms for invalid analogies or comparisons; for example, such false analogies are likened to "comparing grandmothers and frogs" in Serbian and to "comparing apples and oranges" in English.

[edit] Examples

In the field of international relations theory, the fallacy known as the 'domestic analogy' is committed when relationships between political communities (nations) are treated as analogous to relations within political communities (between individuals), such that familiar morals and remedies for interpersonal issues are projected onto foreign policy narratives. To the extent that relationships are different at the local and international level, such analogies are invalid (Hidemi Suganami, The Domestic Analogy and World Order Proposals, CUP, 1989).

Another example is the following:

The universe is like an intricate watch.

A watch must have been designed by a watchmaker.

Therefore, the universe must have been designed by some kind of creator.^[1]

While the universe may be like a watch in that it is intricate, this does not in itself justify the assumption that watches and the universe have similar origins. For this reason, most scientists and philosophers do not accept the analogy, known as the argument from design, with this one specifically known as The Watchmaker Analogy.

By changing a term, the fallacy becomes apparent:

The universe is like an intricate watch.

A watch occasionally needs repair.

Therefore, the universe occasionally needs repair.

The structure of the argument is exactly the same, but we can see that the conclusion does not follow from the two premises.

The false analogy as espoused by William Paley and under its modern guise of intelligent design can be summarised as follows:

We have (A) complex machines which show structure and order. We have (B) a complex universe, natural world and 'biological machines' which also show structure and order. We know that (A) have been created by an intelligent designer (namely us), therefore it follows that (B) must have also been created by an intelligent designer (namely God). This argument could be rephrased as:

All the things in the world we know of, that have been intelligently designed, have certain properties which conclusively demonstrate they have been intelligently designed. It follows then, that anything which also has these properties must also have been intelligently designed.

This is spurious. All we really know for certain is that humans made human artefacts. We don't know for sure that these other 'designed' things are the products of intelligence. This whole argument is circular, it begs the question. It assumes as its premise the conclusion it is trying to demonstrate. In essence it is saying: "Something that is designed has properties which show it was designed." This conclusion, though tautological, is acceptable. The next part of the argument is flawed: "Therefore something which shows these properties was intelligently designed."

All we know for sure, is that when humans design something, it inevitably has properties such as complexity, structure, purpose and order etc., but we cannot demonstrate that this reasoning applies in reverse, that complexity, structure, purpose and order, can only be the product of intelligent design. To do so assumes a priori, that objects which have properties such as complexity and purpose, are designed by an intelligence.