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#### 6.1.2 Addition

- P
- ———–
- P v Q v R v ...

What addition says is that something is already known, so it must be true that that something or something else, or something else, etc. must also be true.

For example, if it is known that ‘`The sky is blue`’, then addition says that it can be inferred that ‘`The sky is blue, or the sky is yellow, or the sky is pink`’, since only one of those statements has to be true.

Addition requires exactly one reference.