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History of Philosophy Book Club Message Board › Reductio ad absurdum - what do you think?

Reductio ad absurdum - what do you think?

A former member
Post #: 75
In formal logic, the reductio ad absurdum is a legitimate argument. It follows the form that if the premises are assumed to be true it necessarily leads to an absurd (false) conclusion and therefore one or more premises must be false. The term is now often used to refer to the abuse of this style of argument, by stretching the logic in order to force an absurd conclusion. For example a UFO enthusiast once argued that if I am skeptical about the existence of alien visitors, I must also be skeptical of the existence of the Great Wall of China, since I have not personally seen either. This is a false reductio ad absurdum because he is ignoring evidence other than personal eyewitness evidence, and also logical inference. In short, being skeptical of UFO’s does not require rejecting the existence of the Great Wall.

It is strange that in natural science, this argument is used all of the time and it is quite legitimate. It is quite powerful when you are dealing with topics and ideas that you cannot prove definitively either one way or other. It is also used by some people who deal with hypothesis testing using statistical inference when their results are inconclusive. And lastly and strangely, Mr. Spock from Star Trek sometimes used this sort of logic to point out what he thought were strange human fallacies in thinking. :)

Do you think it is a severe break in logic?
user 6899431
Group Organizer
Silver Spring, MD
Post #: 121
Ad absurdum arguments appear to be either explicit or implicit conditional statements (your example is explicit). Structurally the consequent is usually negative (in the sense of result), meant to repudiate the antecedent. Here’s an example where the consequent is positive (but nonetheless false): “If taking one daily vitamin is healthy, then taking the whole bottle would be even healthier.” (Note: the person saying this is not being ironic but believes it; ad absurdums are just as popular with comedians as with debaters).

I’m struck by the similarity between ad absurdum and slippery slope arguments. Aside from the grammatical similarity, they both commit the fallacy of begging the question. Here’s an example of a slippery slope: “We need to criminalize marijuana use because it invariably leads to heroin and other drug addictions.”

I think Utilitarians rejected deontological ethics primarily because it lead to ad absurdum statements. Kant said stealing was always wrong, but if that were true, then stealing a terrorist’s plans to bomb your country would be wrong.

You mentioned the productive use of ad absurdums in science. Can you share some examples that aren’t too technical?
A former member
Post #: 76
It is used sometimes when scientist wish to market their research to funding agencies.
What sometimes happens is that a scientist works in one area and then sees correlations in another. He or she then forces a relationship.

One example is:

If there is a significant increase in the frequency of flooding in the United States, then surely this is due to the increase in the mean water level and flooding world wide.

Partially true. Partially false. Other variables are in the mix which are latent and so you have stretched your reasoning.

The person who says something like this is most likely marketing the global warming topic which is hot today.

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