mutability

muuttuvuus The quality or state of being mutable.
(RQ:Fielding Tom Jone)

He did indeed account somewhat unfairly for this sudden change; for besides some hard and unjust surmises concerning female fickleness and mutability, he began to suspect that he owed this want of civility to his want of horses (..)

There rise authors now and then, who seem proof against the mutability of language, because they have rooted themselves in the unchanging principles of human nature.