Simplification rule (Logic)
From Conservapedia
The simplification rule in logic states that where a conjunction of two variables is true then both variables are true individually. In plainer English this means that where a statement using "and" is true the separate parts of the statement are true on their own.
For example if the following is true:
John has an apple and an orange
then the two following statements are also true:
John has an apple
and
John has an orange