Perfect and PluperfectEdit
We next come to the perfect and pluperfect. Here all West-European languages (D E F I S Sc) have a combination of forms of the verb have with a participle, as in E I have lost, I had lost. Similarly in Modern Greek. This is historically developed from sentences in which have and the passive participle retain their ordinary meaning: I have found the key at first meant I have (possess) now the key (as) found; but in course of time this meaning was lost sight of, and the construction was analogically extended to cases in which the same analysis is not logically possible: I have lost the key, etc. Now the corresponding construction would not do in a language of the Esp-Ido type, with an adjectival form of the participle and no indefinite article, because a sentence like me havas perdita klefo (or the plural klefi) would easily be misunderstood as meaning 'I have a lost key (some lost keys)' instead of 'I have lost a key (some keys).' Me havas obliviita omno I've forgotten everything, or I have everything (that was) forgotten. This, in connexion with habits from Polish, his mothertongue, made Zamenhof adopt the really more logical expression mi estas perdinta 'I am having-lost', mi estis perdinta 'I was having-lost' for 'I have (had) lost'; estus estinta would have been. This was at first imitated in Ido (me esas perdinta, me esis perdinta), but to a West-European mind these must always seem clumsy roundabout expressions, and therefore most Idists took readily to the new synthetic forms with inserted -ab-, when these were allowed after some years: perdabis 'had lost', perdabos 'shall have lost', perdabus 'should have lost' (Why perdabas 'have lost' was not adopted at the same time, will ever remain a mystery). Similar insertions had already been used by Courtonne (1885): amavam have loved, amavom shall have loved. But though easier to handle after a little practice, these highly synthetic forms are not attractive, especially when combined with the passive infix -es-: perdesabis 'had been lost', perdesabos, etc., and we must therefore look for simpler expressions.
These are found in combinations, in which the West-European forms are imitated in such a way that all ambiguity is avoided, in the first place because the auxiliary used, ha and had, is different from the full verb of possession, have, haved, and secondly because it is not the participle that is used after the auxiliary, but the crude stem: me ha perda klefe, me had perda klefe 'I have (had) lost a key', which is easily distinguished from me have perdat (perdati) klefe, me haved perdat (perdati) klefe 'I have (got) a lost key, I had (got) a lost key'.
It is easy to form further compound tenses by means of these auxiliaries: vu sal ha perda you will have lost, la vud ha veni she would have come. Note also the infinitive: es plu agreabli tu viva kam tu ha viva o tu sal viva.
It may not be superfluous to mention that ha and had must be used with all verbs, also those intransitive verbs which in D and Sc (and to some extent also in E) are combined with the verb be (sein, være) to form their perfect and pluperfect: lo ha veni he has (is) come, er ist gekommen, han er kommen; lo had veni, etc. Me ha es ich bin gewesen.
It is, of course, possible to form participles of the auxiliaries: hant veni having come, salent veni = Ido venonta. These compound forms may be freely used in apposition, but cannot easily be used as adjuncts in the same way as the Esp-Ido forms can, but then they are not often wanted and relative clauses are always handy. For Z la venonta tempo we say li futur(i) tempe.