We all know that in the indicative mood, we form the pluperfect and the future perfect by using the third principal part, take out the -i ending and add the imperfect/pluperfect tense of "esse." But what is the deal with the simple perfect tense? Why don't we attach the present tense of the "esse" by the same analogy? That is saying: Given amav-eram (I know the dashes should not be there) being the pluperfect and amav-ero being the future perfect, why we say "amavi" rather than "*amav-(i)sum"? It is interesting to see some of the forms sorts of fitting the hypoothesis. amavi vs *amav(i)sum amavisti vs *amaves amavit vs *amavest amavimus vs *amav(i)sumus amavistis vs *amavestis amaverunt vs *amav(i)sunt -> amaverunt (rhotacised,wow!) Is there something that took place right here cause the odd ending in perfect tense? Do they derive from the present tense ending?