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| Tutorial 1 - Simple Arguments | |
A reason is a piece of evidence in support of some claim. A claim is an idea which somebody says is true.
To map a reason, put the reason and the claim in boxes, and link them together. Here is one way to do it:
Examples Consider this piece of reasoning from Apollo Moon Landings:
There should be lots of stars in the Apollo pictures, because if we go out on a clear night and look up, we see many stars. (3.1)
Here, the claim being supported is There should be lots of stars in the Apollo pictures. The evidence is that when we go out on a clear night and look up, we see many stars. Here is how to map this reasoning:
Here is another example:
The 382 kilograms of lunar material brought back to Earth by the six Apollo missions did come from the Moon. Therefore, Apollo astronauts must have landed on the Moon. (9.1-2)
Claim: The Apollo astronauts landed on the Moon.
Evidence: The six Apollo missions brought back to Earth 382 kilograms of material which came from the Moon.
Discussion People use the word "reason" in many different ways. You'll see this if you look it up in the dictionary. In these tutorials, we are using the word in one specific way: to refer to a piece of evidence for a claim.
Technically, a piece of evidence (and hence a reason) consists of a set of claims presenting evidence that another claim is true. Don't worry if that doesn't make much sense right now; it will become more clear in Tutorial 2.
There are lots of superficially different ways to map a reason. The key thing is to visually distinguish the reason and the supported claim, and to show the link between them. The mapping approach we adopt here is the one used in the Rationale™ software. Using this approach show that something is a reason by the use of (a) the colour green, for reason; and (b) the word "because" just above the reason.
Some reasons are good (strong, powerful, valid). That is, they provide strong evidence for the claim. Some reasons are terrible. These tutorials are concerned with the structure of reasoning, not its quality.
New Concepts A claim is a proposition put forward by somebody as true. A proposition is an idea which is either true or false.
A reason is a piece of evidence in support of some claim. Technically, a reason is a set of claims working together to provide evidence that another claim is true.
A claim supported by a reason is called a "contention".
Discussion The word "contention" is technical vocabulary. It is the special word we use for a claim for which some evidence has been provided.
Note that very often, logicians use the word "conclusion" where we are using "contention". Unfortunately "conclusion" is rather misleading in a number of ways.
New Concepts A contention is a claim for which some evidence is presented, whether for or against. Logicians often use the word "conclusion" to refer to a contention.
An objection is like a reason, but is evidence against a contention.
Examples Consider the following passage from Apollo Moon Landings:
There are no stars in the background of the Apollo pictures. Therefore, Apollo astronauts did not land on the Moon. (3.0-1)
Here, we are given evidence against the idea that Apollo astronauts landed on the Moon.
The contention is that Apollo astronauts landed on the Moon; the evidence (which goes against it) is that there are no stars in the background of the Apollo pictures.
Here is a map of the reasoning, showing the objection in red:
Here is another example:
It is not true that there should be lots of stars in the Apollo pictures, because stars can be very faint.
The contention (the thing being objected to) is that there should be lots of stars in the Apollo pictures; the evidence is that stars can be very faint.
Discussion Objections and reasons are very similar; it is just that while reasons present evidence supporting the contention, objections present evidence against it. Roughly, an objection "says why the contention wouldn't be true."
You may have noticed that a reason can be transformed into an objection, and vice versa, if you reverse the contention.
In the mapping approach used here, we show that something is an objection by the use of (a) the colour red, for objection; and (b) the word "but" just above the objection.
Technically, an objection is, like a reason, really a set of claims. This will become more clear in Tutorial 2.
New Concepts An objection is a piece of evidence against some claim. Technically, an objection is set of claims working together to provide evidence that another claim is false.
A simple argument is just a contention with a single reason for it, OR a contention with a single objection to it.
Here are two simple arguments:
Examples
The simple argument is the whole structure (reason AND contention). This is another simple argument, made up of an objection to a contention. Notice that the contention happens to be the same as in the first example; for more on this see Tutorial 3.
Discussion Note that all you need for a simple argument is a single piece of evidence bearing upon a single contention. You don't need both a reason and an objection. In other words, a simple argument is not a debate; it is just an elementary piece of reasoning.
"Simple" doesn't mean small, short or obvious. A simple argument might be quite technical or hard to understand. What makes an argument simple is that it has just one contention and one piece of evidence.
This is important because the simple argument is the basic unit of all reasoning. All arguments, no matter how complex, are made up of simple arguments hooked up together. This will become more clear in Tutorials 3 and 4.
New Concepts A simple argument is just a contention with a single piece of reason for it, or a contention with a single objection to it.
When argument mapping, boxes should contain full, grammatical, declarative sentences.
Examples Use complete sentences, not words or phrases:
CorrectUse declarative sentences, not other kinds of sentences such as questions:
Correct
Discussion It is very tempting to just use a word or simple phrase instead of a full grammatical sentence. This saves effort and space, and you feel as if you have the complete claim in your mind; all you need is a few words to indicate what claim belongs in that place.
However this is wrong. Reasoning is made up of claims, and you can't properly express a claim in anything less than a full grammatical sentence. Using a word or phrase creates a number of problems:
- You might never properly articulate the claim in your own mind.
- Somebody else reading the argument map has to try to guess what claim you had in mind, and often will guess incorrectly.
- As we will see later, without full sentences, you will not be able to apply some important principles of argument mapping.
Generally, using words or phrases rather than full sentences is sloppy thinking.
A declarative sentence is one which states a proposition which can be true or false. Some kinds of sentences are not declarative; for example, questions don't state propositions. Reasoning is a matter of the logical or evidential relationships among propositions, so you should always be using declarative sentences to express reasoning.
New Concepts A declarative sentence is one which states an idea which can be true or false.
You should avoid putting reasoning in boxes. In an argument map, boxes contain claims, not whole arguments.
The Apollo astronauts could not have survived the journey through the Van Allen Belt, so they cannot have been to the Moon. (6.4)
This box contains a simple piece of reasoning.
The correct way to map the argument is to display the reasoning.The shadows in the Apollo images seem to point in different directions, suggesting that artificial lighting was used when they were taken. Therefore they were taken in a studio on Earth. [Based on 5.1]
The reason here contains a simple argument. This means that there are two separate arguments being made.
Map each argument separately.
Discussion The whole point of argument mapping is to make the structure of reasoning completely explicit using graphical techniques such as boxes and arrows. If reasoning is inside a box, it is to some extent hidden away.
This is not just being pedantic. In following tutorials you'll see that many critical argument mapping techniques cannot be used unless and until we have fully revealed the structure of the reasoning.
Key Points
Note: don't put reasoning inside a box. Argument maps display the structure of reasoning; don't hide that structure inside a box.
New Concepts A claim is a proposition put forward by somebody as true. A proposition is an idea which is either true or false.
A reason is a piece of evidence in support of some claim. Technically, a reason is a set of claims working together to provide evidence that another claim is true.
A declarative sentence is one which states an idea which can be true or false.
A conclusion is a claim for which some evidence is presented, whether for or against. See also contention.
An objection is a piece of evidence against some claim. Technically, an objection is set of claims working together to provide evidence that another claim is false.
A simple argument is just a contention with a single piece of reason for it, or a contention with a single objection to it.
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Last updated 28-Aug-2007
