gives access to an earlier stage, at least in some details, of the languages being compared, which can be valuable since the more time has passed, the more changes have been accumulated in the structure of a living language. Thus, the earliest known attestations of languages should be used with the comparative method.

Internal reconstruction, when it is not a sort of preliminary to the application of the comparative method, is most useful if the analytic power of the comparative method is unavailable, especially in language isolates.