Problems that a theory of linguistic
change must answer.
The constraints problem
In what linguistic and social conditions
are certain changes likely or unlikely?
The transition problem
What intervening stages "can be observed, or
must be posited, between any two forms of a
language defined for a language community at
different times?
The embedding
problem
How are changes embedded in the matrix
of linguistic and extralinguistic
concomitants of the forms in question?
The evaluation problem
How can the observed changes be evaluated - in terms of
their effects upon linguistic structure, upon
communicative efficiency, and on the wide range of
nonrepresentational factors involved in speaking?