This is a Griemas Square

It was developed by Algirdas J. Greimas and is a model used for semiotics. However, it's also a handy tool for theme building. Each letter represents a relationship within the model. The simplified version is:

1. the positive
2. the contrary
3. the contradiction
4. the contradiction of the contrary (or the negation of the negation)

If you've read Robert McKee, you may recognize this. You may also remember this from Aristotle (who Greimas built his square from). His was called the square of opposition, which broke down:

1. Universal affirmative: All S are P
2. Universal negative: No S is P
3. Particular affirmative: Some S are P
4. Particular negative: Some S are not P

The nice thing about this is that it can show you the extremes of a thematic idea you are playing with.

For example, if you were looking at the theme of change, you could say:

1. Change can happen.
2. Stasis can happen.
3. Stasis can't happen.
4. Change can't happen.

These statements then become jumping-off points for what they mean.

1. Let's stay with change can happen
2. Let's say that stasis can happen along with change.
3. This almost sounds like constant, chaotic change—which may not be good.
4. This certainly sounds more direct and conclusive. Change doesn't exist at all—which means we are trapped.

This is just a simple example, but using the notion of extremes to investigate the positive and negative edges reveals the directions your main characters take or the roles of other characters within your story (i.e. a character who believes no one can change, not even themselves).

So if you are ever working on the theme and unsure exactly where that theme can go or what different worldviews can be embodied, using the Greimas helps you explore the edges.