True Value and NOT
It is possible to acquire a new proposition by prefixing it with NOT. If the first proposition is "that flower is red," then NOT "that flower is red" denies the first proposition; "that flower is not red." This is the simplest way to acquire a new proposition from the old one. Let us think about the effect that an old proposition's truthfulness gives to the new proposition's. When an old proposition is indicated with A, then a new proposition can be expressed with NOT A. If A is false (F), then NOT A is true (T). This also applies in reverse order as shown below.|
The diagram above is called a "Truth Table," assuming that T and F are the values of propositions. The following formula can be constructed by considering the equal signs and paying careful attention to the truth value.