Table 5
| 1 | 1 and 1 = 6 |
| T | T |
| F | F |
We know that 6 is true if and only if 1 is true. In other words, the statement “1 and 1 if and only if 1” is true, no matter what statement 1 may refer to. It is because of this fact that we never use a statement in the form “1 and 1”: it can always be replaced by the plain statement “1.”