As in…
“Carbon Dating is based on circular reasoning”.
Don’t know about carbon dating, but here’s a shot at circular reasoning, taken from a song I used to sing to my little girl:
There’s a hole in the bucket, dear Liza, dear Liza.
There’s a hole in the bucket, dear Liza, a hole.
Mend the hole then dear Georgie, dear Georgie.
Mend the hole then dear Georgie, dear Georgie, the hole.
With what shall I mend it, dear Liza…
With the straw, dear Georgie…
The straw is too long, dear Liza…
Then cut it dear Georgie…
With what shall I cut it dear Liza…
With the knife, dear Georgie…
The knife is too dull, dear Liza…
Then sharpen it, dear Georgie…
With what shall I sharpen it, dear Liza…
The stone, dear Georgie…
The stone is too dry, dear Liza…
Then wet it, dear Georgie…
With what shall I wet it, dear Liza…
With water, dear Georgie…
In what shall I get it, dear Liza…
In the bucket, Dear Georgie…
There’s a hole in the bucket, dear Liza, dear Liza.
There’s a hole in the bucket, dear Liza, a hole.
That used to make her laugh and laugh! 
A duck!
(Someone had to do it.)
[the lucky duck obediently appears]
As I understand it, the carbon dating circular reasoning goes something like this:
Q. How do we know that carbon dating is accurate?
A. Because we tested it on other things that we know how old they are.
Q. How did you know how old those other things were?
A. Because we tested them.
Q. How did you test them?
A. With carbon dating.
I can’t explain circular reasoning to you because you don’t understand it.
You don’t understand circular reasoning becasue I can’t explain it to you.
In the first sentence fact A (I cant’ explain CR to you) is supported by the fact B (you dont’ understand it)
I then support fact B with fact A.
I hope that helps.
Note: The carbon theory example is a claim – there are plenty of non-circular confirmations.
Circular reasoning means you believe A because of B, and you believe B because of A. There can be as many links as needed, but it all adds up to the same thing.
I believe in God because the bible says he/she exists. How do I know the bible is correct? Because God wrote it.
A chicken was required to produce the worlds first egg.
Where did that chicken come from?
From an egg, of course.
It’s like a catch-22, only inside out or something.
Of course, circular reasoning can also happen to lead to a correct conclusion. An example from a popular website: Cecil Adams is the world’s smartest human being. How do we know this? Because he tells us so. Why can we take his word on it? Because he’s the world’s smartest human being, and the world’s smartest human being wouldn’t lie to us. Of course, it happens that despite the circular reasoning here, Cecil Adams is, in actual fact, the world’s smartest human being.
By the way, if you’re still wondering about carbon dating, carbon dating is primarily calibrated via tree-ring dating, and tree-ring dating is calibrated by about a bazillion farmers planting trees and counting how many years it is before they cut them down. Just don’t ask how those farmers are calibrated.
Circular reasoning is also known as “begging the question”, or, for logicians, “petitio principii”.
My favorite example from real life came from a course in Comparative Religions in which a student’s paper contained the assertion that Jesus of Nazareth was taken for his execution to a place called Golgotha, which means “The Place of the Skull”, so named because it was the place where Jesus was crucified.
Apparently some people consider begging the question and circular reasoning to be two slightly different things. I started a similar thread many moons ago. The discussion get a little confusing but its worth a look.
“Begging the question” isn’t necessarily the same thing as circular reasoning.
“Begging the question” is when you presuppose the answer to a preliminary question you haven’t thought to ask. For instance, city planners insist on asking developers “but where is everyone going to park?” That assumes that everyone is going to drive to the development. The correct question to ask first is, “how are people going to travel to this development?” Only when you have determined how many people will be driving to the development do you have to start worrying about parking, if at all.
I like this, it makes my head spin:
“What’s the difference between a valid deductive argument and a fallacy? In the case of the fallacy of
circular reasoning, the difference is not be as obvious as you might expect. In the fallacy of circular reasoning,
which is often called begging the question, you assume to be true what you are supposed to be proving. But
that’s also true for all valid deductions, where the conclusion (what you are trying to prove) is derived from the
premises or assumptions. This difference is that, in circular reasoning, the conclusion is contained in a single
premise or assumption, while in a deductive argument the conclusion is derived from both premises.”
I’m gonna do cocaine, so i can work harder, so I can make more money, so i can buy more coke, so i can work harder, so i can make more money, so i can buy more coke…
“Elijah the Prophet reveals himself to my rabbi”
“How do you know this is so”?
“My rabbi said so specifically”
“Maybe he is lying”
“What!?! You think Elijah the Prophet would reveal himself to a liar???”
Thank Goodness ! G.W. Bush will restore honor and morality to the Presidency so that once again the American people can respect the highest office in the land.
“This song is called Alice's Restaurant.' It's about Alice and the restaurant, but Alice's Restaurant is not the name of the restaurant; that's just the name of the song, and that's why I call the song Alice’s Restaurant.’”
- Arlo Guthrie
Good example, Mack (as were others, BTW).
I’ll have a go!
Let’s start with Circular reasoning and then look at some of the other subjects that have come up.
There’s some jargon coming up, but it’s not scary so you don’t have to turn into a philosophy geek to get it.
In a well-formed logical argument, you have two or more premises (statements you start with) and a conclusion (the statement you end up with). One simple form of this kind of reasoning is called a syllogism, and here’s an example:
- Only smart people post to the SDMB
- Doc Moss posts to the SDMB
Conclusion: Doc Moss is smart.
You might think the conclusion follows pretty obviously from statements (1) and (2), and it does. It is possible to analyse exactly why it does follow, in a very formal and mathematical way, and this is what people who study logic do all day. No need to go into it here!
The thing to note is that the conclusion follows from the premises, but neither of the premises contains the conclusion. You can look at either (1) or (2) all you like and you won’t see the conclusion.
Now, if a premise involved in the argument either contains the conclusion, or is directly equivalent to it, you have what we call ‘circular reasoning’. Here’s a very obvious example. In fact, it’s so obvious it looks dumb:
- Doc Moss has assessed that only smart people post to the SDMB
- Doc Moss posts to the SDMB
Conc: Doc Moss is smart
Like I said, this example is so obvious it looks dumb, and it is. Obviously, Doc Moss’s assessment is only any good if Doc Moss is smart… so the argument is flawed.
But there are many chains of reasoning where the mistake isn’t so obvious. Here’s one which has caused a lot of controversy over the past few centuries:
- The bible tells us it is the word of God
- God is infallible and truthful
Conc: The bible is infallible and truthful
Here, it’s not so obvious quite where the reasoning goes wrong, until you think about (1) for a while. Look at those words ‘tells us’. These words contain a hidden implication that what the bible tells us is true… but that is what the argument is trying to establish! Hence we may regard this as circular reasoning.
So there you have it: circular reasoning is reasoning in which the conclusion is fully contained in at least one of the premises.
What about carbon dating? Well, the ever-reliable and illuminating Duck Duck Goose has hit the nail on the head. Some critics of CD think it is based on circular reasoning, like this:
- We can test carbon dating on old artefacts
- Carbon dating comes up with fairly accurate results
Conc: Carbon dating is fairly accurate
Now if in (1) the phrase “old artefacts” means “artefacts whose age has been established through carbon dating”, then this is circular reasoning. However, as others have pointed out, the evidence in favour of carbon dating is much more sophisticated than this kind of trite and slly argument.
What about begging the question? Similar to circular reasoning, but with the obvious difference that it pertains to a more question-and-answer type of debate. Example:
Doc Moss: “Is every Doper smart?”
Ianzin: “Of course! They all are!”
Doc Moss: “How do you know?”
Ianzin: “Because only smart people post to the SDMB”
At which point Doc Moss would be entitled to exclaim, “But that begs the question!”.
And finally, what about a Catch-22 situation? A ‘Catch-22’ involves two conditional statements (following the ‘if… then…’ pattern). They are constructed so that at least one outcome - the one you want - can never be achieved. In Joseph Heller’s wonderful novel, ‘Catch-22’, the hero (called Yossarian) is a bombardier who has flown many dangerous bombing missions and doesn’t want to fly any more in case he gets killed. Yossarian asks the medic how he can get permission not to fly any more missions, and he is told the only way is to be declared insane. However, it is explained to him that not to want to fly any more missions is, in itself, as sign of sanity. So…
- If you are insane, then you will be permitted not to fly any more dangerous bombing missions
- If you want to stop flying dangerous bombing missions, then you must be sane
Catch-22!
Probably the most obvious real life example that most of us face at some stage is…
- If you get some experience, then we can offer you a job
- If you get a job, then you’ll gain experience
Over and out.
“Our society is based on the traditional values that our society is based on”
and the ever concise
“Sin is sin”