A recent thread touched on the question of whether Slavic aspectual pairs should be considered part of the same lexeme or not.
I wonder if the same logic can be applied to the principal parts of Latin or (especially) Greek verbs. For example, take the following array of verbs from Greek:
peítho: (present active) "I persuade", pépoitha "I trust, rely on" (perfect active), pépeismai "I believe, trust" (perfect passive)
Is it really clear that these forms constitute the same lexeme, any more than a Slavic aspectual pair like Slovenian postavljati / postaviti ("to place") are the "same" lexeme?
Can "lexematicity" be viewed as a measure of the degree of linkage between forms, rather than a matter of "either-or" connection?