What does it mean for an argument to be coherent?
March 25, 2012 7:02 PM   Subscribe

What does it mean for an argument to be coherent?

What does it mean for an argument to be coherent? Are all bad arguments incoherent? Does anyone know of a concise resource that does a crash course on the basics of this stuff, i.e. how to read and evaluate an argument?
posted by polymodus to Writing & Language (18 answers total) 7 users marked this as a favorite
Typically, when someone says an argument is coherent, it means they think it makes sense on a fundamental level; recognizes all available and known facts; and is internally consistent (I.e. the evidence presented actually supports what's being proposed). It may or may not be correct, but at least it's plausible and worthy of discussion and consideration.
posted by Cool Papa Bell at 7:11 PM on March 25, 2012 [1 favorite]

My recollection is that syllogisms which are structured correctly can be considered coherent but still fallacious.
posted by dfriedman at 7:11 PM on March 25, 2012

I doubt that "coherent" has a rigorous meaning. I think it's just another way of saying "makes sense".
posted by Chocolate Pickle at 7:13 PM on March 25, 2012

This is kind of a vague question, but I'll take a shot. An argument is said to be coherent if it hangs together, if the planks in its platform make sense taken as a whole; that is, no individual item in the argument contradicts the others. A bad argument may be coherent (i.e., its parts may be consistent but it may still be wrong due to inherent incorrectness). I'd look into guides to debate and discussions of common logical fallacies like strawmen/begging the question/over-generalization.
posted by axiom at 7:15 PM on March 25, 2012

You talkin' to me? is on my to-get list.
posted by pantarei70 at 7:21 PM on March 25, 2012

I agree that there's no technical definition of coherent - at least I'm not aware of one.

An argument is valid if it obeys the rules of logic and invalid if it breaks them, but validity does not indicate veracity.

In everyday conversation, if someone were to say than argument was incoherent I would take that to mean that it most likely included some sort of non sequitur or a conclusion that doesn't follow from the premises. "Penguins love the antarctic, and that proves that climate change is made up" or something like that.
posted by kavasa at 7:31 PM on March 25, 2012 [1 favorite]

Does anyone know of a concise resource that does a crash course on the basics of this stuff, i.e. how to read and evaluate an argument?

The logical fallacies which axiom mentions will get you part of the way there, but the background to those fallacies is symbolic logic, which allows you to know if the structure of an argument is sound gardless of the argument's content.

It's not at all concise, but I thought Robert Baum's textbook Logic was very clear and easily understood. Granted, I read it 20 years ago and it's undoubtedly gone through many editions since then, but I really loved that book. I did not love Baum as a professor, though; he had a monotonous voice which made his lectures downright painful.
posted by johnofjack at 7:34 PM on March 25, 2012 [2 favorites]

To me, the biggest feature on an incoherent argument is one where point #1 contradicts point #2 (or #3, or #4...). To say an argument is incoherent is to say that it's an argument that manages to disprove itself if one were to fully consider the implications of the points.
posted by the jam at 7:38 PM on March 25, 2012

Jim Pryor has some very useful pages on this for his intro philosophy students.

The term "coherent" might mean something specific to some people.... but I won't speculate about exactly what it might mean.

One place to start would be with some terms from deductive logic. (These terms are used in looser ways by the general population but here I'm talking about their formal meanings in logic and philosophical discourse.)

(1) An argument can be deductively valid. This means that the conclusion follows from the premises. Put another way: if the premises are true the conclusion is guaranteed to be true. (Notice, this just says "if"... which means that an argument can be valid but have false premises. In that case, the conclusion is not guaranteed to be true. All that validity tells you is that the premises fit together in a certain pattern that yields the conclusion; validity is only a comment on the logical form of the argument, not on the truth of its contents.)

Here are two examples of valid arguments. Notice that what they have in common is their form.:

All men are mortal.
Socrates is a man.
Therefore Socrates is mortal.

All men are ten feet tall.
Socrates is a man.
Therefore Socrates is ten feet tall.

(2) An argument can be sound. A sound argument is a valid argument with true premises.
Notice this means the conclusion of a sound argument is guaranteed to be true.

(3) A fallacious argument, one that includes a logical fallacy, is deductively invalid. This means that the truth of its premises would be no guarantee of the truth of its conclusion. (A fallacious argument can use true or false premises. Again, fallaciousness or invalidity is solely a comment on the form of the argument, not on its contents.)

An example of a fallacious argument:

All men are mortal.
Socrates is located in Greece.
Therefore Socrates is mortal.

(Notice, the premises might be true in that one, but they don't "fit together" in the correct way to yield the conclusion. Even if the premises are true, they don't guarantee the truth of the conclusion. We would need an additional premise that says: all entities located in Greece are men.)
posted by LobsterMitten at 7:39 PM on March 25, 2012 [6 favorites]

And link to Jim Pryor should really go here: Pages for beginning philosophers on how to evaluate an argument. And his Vocabulary describing arguments.
posted by LobsterMitten at 7:47 PM on March 25, 2012 [1 favorite]

Usually a claim would be called coherent iff it does not entail a contradiction (since a contradiction would be incoherent). It would be easy to extend that notion of coherence to an argument: call an argument coherent iff its premises and conclusion do not entail a contradiction.

My guess, though, is that what you're really interested in is validity, as LobsterMitten has already explained.

(The reason I'm guessing you're not after mere coherence is that the following argument satisfies that criterion: "It is Sunday. Therefore, the table is brown." The argument is coherent insofar as neither the premise, the conclusion, nor their conjunction entail a contradiction. But it's still a terrible argument. Why? The premise doesn't support the conclusion.)

In addition to Jim Pryor's pages, already linked, I'd recommend Anthony Weston's A Rulebook for Arguments. It's a short handbook with some simple rules regarding both deductive and inductive argumentation. Depending on your specific needs, it may be very useful.
posted by voltairemodern at 7:51 PM on March 25, 2012

My favorite logic quote is from, I think, Quine: "Validity is not a term of praise".
posted by thelonius at 7:58 PM on March 25, 2012 [1 favorite]

Under my subjective definition, an argument is coherent if it articulates its premises and explains its reasoning, and is internally consistent and progresses logically.

What makes an argument "good" (or "coherent") might depend on the discipline within which the argument takes place. But I certainly think an argument can be "bad" while still "coherent" -- for example, if it is wrong, such as because it relies on flawed premises.
posted by J. Wilson at 8:00 PM on March 25, 2012

I construe "coherent argument" more narrowly than Cool Papa Bell, for instance.

An argument could be coherent but be based on faulty premises, or fail to address counter-evidence. To my ear, "coherent" means that the chain of reasoning is clear. At no point in your argument do you say "look, a unicorn!" You don't pull in fallacies like ad-hominem attacks or appeals to authority.
posted by adamrice at 8:23 PM on March 25, 2012 [1 favorite]

A logically flawed argument can still be coherent. Here's a litmus:

Typical response to valid argument: "That is correct"
Typical response to coherent but flawed argument: "That is incorrect, because of XYZ"
Typical response to incoherent argument: "What"

As mathematicians are fond of saying, "That's not even wrong."
posted by qxntpqbbbqxl at 8:32 PM on March 25, 2012 [7 favorites]

I'll second the recommendation of Anthony Weston's A Rulebook for Arguments. Used copies should be available very cheaply.
posted by LobsterMitten at 9:10 PM on March 25, 2012

Coherent doesn't mean that it is a correct argument, it only means that you can follow the logical steps.
posted by JJ86 at 6:14 AM on March 26, 2012

A recent post in the blue provides a very good answer to your question: A series of short animations explaining critical thinking. Created for children and pretty good for adults too.
posted by alms at 1:11 PM on March 26, 2012

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