Laws of thought:

 

Since Aristotle (at least) we have had a tradition of recognizing certain laws of thought. These laws, or rules, seem to work in virtually every language game we play. That seems to include those games within which we describe our metanarratives.

 

For a relatively modern expose of this see Peirce.

 

  The first rule is the rule of identity: What is, is.

  The second is called the law of non-contradiction: Nothing both is and is not.

 

Aristotle does point out that Heraclitus disagreed with this. But there are those that disagree with him, of course. There is a lot of more current work that seems to avoid this issue.

 

  The third rule is the rule of the excluded middle: Either one or the other. Not the other? Than the one.

 

But it is what you say that is true or false. And it seems today that the main reason this is so is because of the nature of the language game and the rules you are following. But we can ignore this complication to start with and look at the kinds of things you might say, regardless of what game you are playing.

 

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