Few things are as immutable as the addiction of political groups to the ideas by whichthey have once won office.

-Galbraith,John Kenneth
  The Affluent Society.

It wasn't by accident that the Gettysburg address was so short. The laws of prose writing are as immutable as those of flight, of mathematics, of physics.

-Hemingway, Ernest Millar
  Letter, 23  Jul.

God made thee perfect, not immutable.

-Milton,John
  Raphael to  Adam. Paradise Lost (published1667), bk.5, l.524.