question about absurdum ad reductio

Delirium

Sorry if this isn't the right forum, mods.

I was looking to get a better understanding of absurdum ad reductio when used in discussions/debates.

I've seen it used a couple of times in threads, but to be honest, I'm left scratching my head more often than not as to what the point of the post was.

So could anyone help understand the purpose of it?

raah!

If you mean reductio ad absurdum (I don't know about latin or what difference the order makes, this is just the form I have normally seen it in, and translated to "reduction to absurdity"... or something) then this is essentially just a proof by contradiction.

It proves that a proposition is true by showing that the opposite of the proposition is contradictory, and therefore not logically possible to maintain.

So if something is either true or false, and it's impossible that it be false (because it's being false leads to a contradiction or "absurdity") , then it's true.

Delirium

raah! wrote: »

If you mean reductio ad absurdum (I don't know about latin or what difference the order makes, this is just the form I have normally seen it in, and translated to "reduction to absurdity"... or something) then this is essentially just a proof by contradiction.

Don't know latin either, but yes, that's the idea I was looking to get a better understanding of

It proves that a proposition is true by showing that the opposite of the proposition is contradictory, and therefore not logically possible to maintain.

So if something is either true or false, and it's impossible that it be false (because it's being false leads to a contradiction or "absurdity") , then it's true.

Thanks for the explanation.

Does it also work, if for example, someone states proposition A.

Then a person arguing against A then uses proposition B (which might be similar to A) as the "absuridity" example.

They're not using an opposite of something, but taking a similar concept (B) and saying because that is "absurd", A isn't a good idea.

raah!

This would be a lesser argument with a similar form. But it wouldn't be a logical proof that you can't hold proposition A.

The argument there would be along the lines of "what you are doing is what nazi's also did, and they are bad". It's not a bad argument, but it's not a logical proof. This second argument depends on the way in which A is similar to B. If it was for example "nazis also wore hats" then it's not a good example, because this is not the way in which B is "absurd" or "wrong" or whatever you want.

If you show B is logically entailed by A, and that B is something ridiculous (i.e contrary to commonly held beliefs about the world/commonly held beliefs about what is right or wrong) then you have a good argument.

Black Swan

koth wrote: »

Sorry if this isn't the right forum, mods.

Your topic is welcome.

krd

Reductio ad absurdum, as a logical fallacy in argument, is to reduce a position to absurdity.

Like, someone may argue in favour of homosexual marriage "all adults should be allowed to marry who they love"

And the reactionary Catholic priest will retort "if we let that happen, then women will marry dogs" - there was a German priest who made this point.


Reductio ad absurdum, underlines the fallacy of taking logical reasoning to extremes, to validate or invalidate a position.

Logic in itself, is a crock.

raah!

What? Proof by contradiction is a logical fallacy? That's completely wrong. The priest in your example did not use any logical reductio ad absurdum.

If you think logic is a crock, and obviously you know nothing about it; then don't talk about it.

Delirium

raah! wrote: »

What? Proof by contradiction is a logical fallacy? That's completely wrong. The priest in your example did not use any logical reductio ad absurdum.

may I ask why it doesn't fall under reductio ad absurdum?

Still trying to understand the concept, and wondering why the priest example isn't an example of it.

raah!

What he gave was an attempt at a reductio, but the argument was invalid:

The premise is:
-all adults should be allowed to marry who they love
But this does not entail:
-if we let that happen, then women will marry dogs

The preist makes a claim about what will happen, which is nowhere entailed by anything in the premise, or mentioned. The premise mentions should. Furthermore the priest interprets 'who' to be possibly referring to dogs. Which is also questionable.

So he's not taking the premise to a logical conclusion. He's saying some unrelated sentence.

If he wanted to attack the premise with a reductio ad absurdum he could say:
-all adults should be allowed to marry who they love
and then go to:
-all adults should be allowed to marry children (who they love)

And if the person who made the claim, or society in general, find it objectionable that all adults should be allowed to marry children, then they have to find the earlier premise objectionable.

They have to unless they are incapable of proper reasoning. The point of the original premise could be safeguarded from such logical attacks by making it more precise like:

-All adults should be allowed to marry which ever adults they love.


So in summary, the preist example is an attempted reductio, but since his argument was invalid it was not "logically following a proposition to its conclusion".

In krd's post he also says "following something logically to its conclusion is a logical fallacy". That's a blatantly contradictory statement. He's saying "being logical is illogical". This is a result from taking the things you hear people trotting out in place of actual arguments too seriously.

Delirium

Thanks for the great explanation, it's much appreciated