The stone from "The Stone" symbolizes "a representation of things that do not grow or change "
Explanation:
The stones are generally seen as something which is stable and grounded to earth, as being considered a motionless element this can not represent achievements, enemies to defeat, or problems, but it could be easily seen as something that does not change due to its permanence, stones can remain for long periods in the same place without showing any visible change.
They had to stay on topic. if they strayed to far people might not understand them. AND the entire goal of the Declaration of Independence was to bring the countries together so they understand.