I believe that argument maps as I understand them are superior to other types of argument diagrams. I will describe four different kinds of argument diagrams, then explain why argument maps seem to be the best.
Four different kinds of argument diagrams.
The four types of argument diagrams are Hurley diagrams, Toulmin diagrams, ordinary argument diagrams, and argument maps. In order to understand how they differ, let’s consider a supporting argument and objection they can all represent.
First, let’s consider the supporting argument:
- Socrates is a man.
- All men are mortal.
- Therefore, Socrates is mortal.
Hurley diagrams are briefly taught in the most popular logic textbook: A Concise Introduction to Logic by Patrick Hurley.
Each circle represents a different statement of the argument. The statements of the argument were already numbered above. 1 and 2 are the first two premises, and 3 is the conclusion. The bracket makes it clear that both premises are a single argument for the conclusion.
Note that Hurley diagrams are not capable of representing a supporting argument and objection at the same time.
Toulmin diagrams require that we don’t simply give deductive arguments, and that some sort of justification is discussed other than a mere deduction. For that reason we write down the “grounds” that support the deductive premises. The deductive premises are mentioned in the “warrant” area. The conclusion is written as the “claim.”
Notice that Toulmin diagrams don’t make it clear when we have an extended argument. Sometimes a specific premise is justified by an argument, but this diagram does not make it clear when a specific premises is supported by an additional argument. In the specific case of this argument the grounds is technically a justification to the premise that states “all men are mortal.”
Ordinary argument diagrams
Ordinary argument diagrams are almost identical to Hurley diagrams. Just like the Hurley diagrams, each circle represents a different statement, the first two circles represent the premises, and the final one represents the conclusion. The main difference is that a line is often used to make it clear that the premises support the conclusion instead of a bracket. Additionally, ordinary argument diagrams are capable of modeling both arguments and objections within a single diagram, which Hurley diagrams can’t do.
Argument maps are much like ordinary argument diagrams, except the statements are written in boxes, the boxes are labeled, the arrows are labeled, and premises are given a color. It is made clear that both premises are a single argument for the conclusion because they are connected by a curved line that leads to a single arrow. We know that the premises are given as a reason to believe the conclusion because the term “supports” is written alongside the arrow.
Now let’s consider how the four different diagrams can represent an objection to a supporting argument.
The supporting argument is the following:
- If Socrates is a dog, then Socrates has a tail.
- Socrates is a dog.
- Therefore, Socrates has a tail.
The objection to the supporting argument is the following:
- Socrates is a human.
- No humans are dogs.
- Therefore, Socrates is not a dog.
Hurley diagrams are incapable of representing objections as distinct from supporting arguments. It’s not possible for them to represent a supporting argument and objection within a single diagram.
The Toulmin model requires that we give additional support to the supporting argument because it requires more than a mere deduction from premises, it asks us to give a qualifier (that not all dogs actually have tails because it could be removed), and it is capable of giving the objection in the “rebuttal” section.
However, note that the Toulmin model does not make the following clear:
- The “grounds” is an additional argument to the premise that states that “if Socrates is a dog, then he has a tail.” This would be useful information, but it’s not provided.
- The objection is technically against the premise that states “Socrates is a dog.” This would be useful information, but it’s not provided either.
The ordinary argument diagram is also capable of representing the supporting argument and objection simultaneously, and it is capable of making it clear that the objection is against a specific premise (premise 2: Socrates is a dog). Premise 4 and 5 are the premises of the objection. In this case the objection has an arrow with a strike through it, which is pointing towards the premise they are against. It is clear that there is a single objection consisting of two premises because of the line that connects both of the premises.
The argument map is capable of representing the positive argument and objection within a single diagram. The boxes containing the objection are pink to make it clear that they’re part of an objection, and the word “opposes” is written alongside the arrow to make it clear that they are against a specific premise that the arrow points to. It is clear that the objection consists of a single argument with two premises because there’s a line connecting them both to a single arrow.
Why argument maps seem to be the best.
Just based on the argument diagrams above, argument maps are capable of doing everything the other diagrams do, but they are much easier to read because of the colors, the fact that the premises are written in boxes, and because the boxes and arrows are labeled. In particular, argument maps can help make the following clear:
- when multiple premises form a single argument.
- when a statement is a premise or a conclusion.
- what statement is supported by premises.
- when premises are used as an objection.
- what specific statement an objection is against.
Of the four types of diagrams, Hurley diagrams and Toulmin diagrams are the most inferior:
Hurley diagrams make it clear when there are multiple premises for a single argument, when a statement is a premise or conclusion, and what statement is supported by premises. However, it doesn’t tell us what premises are used as an objection or the specific statement the objection is against.
Toulmin diagrams can tell us when multiple premises form a single argument, when a statement is a premise or conclusion, and when premises are used to form an objection. However, Toulmin diagrams don’t always tell us when a specific statement is supported by an extended argument, or what specific statement an objection is against.
Here is a table that summarizes many of the results:
|A reason to favor the type of diagram.||Hurley diagrams||Toulmin diagrams||Ordinary diagrams||Argument maps|
|The statements are written on the diagram.||No||Yes||No||Yes|
|It states when multiple premises form a single argument.||Yes||Yes||Yes||Yes|
|It clarifies when a statement is a premise or conclusion.||Yes||Yes||Yes||Yes|
|It clarifies what specific statement is supported by premises.||Yes||No||Yes||Yes|
|It states when premises are used as an objection.||No||Yes||Yes||Yes|
|It clarifies what specific statement is opposed by an objection.||No||No||Yes||Yes|