Books themselves need no defense. Their spokesmen come and go, their readers live and die, they remain constant. Lawrence Clark Powell
Political assumptions can remain constant for long periods and then change very quickly. Jacob Weisberg
Become a student of change. It is the only thing that will remain constant. Anthony J. D'Angelo
And within the world that you've created, the physics of that world have to remain constant they can't be amorphous and changing. Bill Sienkiewicz