Home / Tutorial 2	Up
Exercise 2.1 Model Answer

This argument map was the model answer in Exercise 1.1.

Exercise 2.1 is to produce a full argument map showing all co-premises.

How did I get from the problem to the solution?  There are quite a few steps; lets walk through them slowly. 

Roughly speaking, we need to know what we're going to put in the empty co-premise box in this diagram:

(Note that we might want to have two or more additional co-premises, but for the moment lets work with one and see how far we get.)

The claim that goes in the empty co-premise box is going to help tie the premise to the contention, and it will do that by sharing terms or concepts with them. So, important clues about what the co-premise might be comes from looking at those other claims. 

The first thing to do is to see if the Rabbit Rule is satisfied (it won't be).  Are there any significant terms or concepts in the contention which don't appear below it? Lets run through them:

So "artificial lighting" and "used when taking" are going to have to appear in some additional co-premise.  For convenience, lets throw them in right now:

Don't worry that we haven't made a proper sentence yet; well do that later.

The second step is to look in the other obvious place for clues: the main premise.  Here we apply the Holding Hands rule. Are there any significant terms or concepts which appear there but not anywhere else (and in particular, not in the contention)?  Again, we'll just run down the list:

So we have three more things which are going to have to appear in some additional co-premise.  Lets throw them in; then we'll have all our raw materials assembled in one place:

Out of these raw materials we're going to build a sensible co-premise so that we end up with a properly structured argument.

One thing to notice right away is that Apollo really goes with pictures (its the Apollo pictures we're talking about, after all), and pictures is in the contention, so we should stick Apollo up there with it:

That was really just a matter of housekeeping.  But now we face a more interesting challenge: what sensible co-premise(s) do we construct out of the raw pieces we've got remaining?

In this case, it jumps right out; the pieces are almost a coherent sentence already.  What about

Artificial lighting must be used when taking pictures to make shadows point in different directions.

All I've done is add a few "filler" words to help the raw materials hang together in a sensible way. So, plugging this sentence into the argument map, this is what we get:

Now do a quick check:

• Are there any danglers?.... No
• Does the whole thing make sense?.... Yes

Then we're done!  This is now a proper argument map of a well-structured simple argument.

One thing to notice: the co-premise is not necessarily true.  In fact, it is a weak point in the argument; that is where it is going to be attacked with objections.  The important thing we've done here is to identify what it is. 

 Last updated 06-Jul-2007