-miş provides the distinction between the two English past tenses “simple past tense” (i went) and “present perfect tense” (i have gone). The Turkish past tenses simply tell that the action (has) happened in the past, they don't tell whether it has been completed/reversed/undone at present time or not. For example: Turkish Verb: gelmek / English Verb: to come / Positive Definite: geldi / Positive Indefinite: gelmiş / Negative Indefinite: gelmemiş or, Elim kesilmiş = my hand is cut (i didn't see or notice it until now).