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1.1 Reasons

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:

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.

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.

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.