In the choice of grammatical terminations the statistical method, which served us for the purpose of the vocabulary, cannot be strictly applied, because living languages diverge too much in this matter. Nevertheless it does not leave us entirely in the lurch.
Such cases as the dative and genitive and also the ablative, etc., must be expressed by prepositions in conformity with the tendency of Western European languages. It is advisable to have an inflection for the accusative, although this is only intended for occasional use, because in the great majority of instances there is no necessity to distinguish it from the nominative. As neither the Romance languages nor English and Scandinavian possess any accusative inflection, and as the Slavonic languages do not give us any help here, we are obliged to fall back on German, which in the feminine and neuter has no inflection. The masculine, however, in many cases has an -n (den guten knaben). The fact that this termination is also mostly used for the dative, as well as for the infinitive, need not prevent us employing it in our language for the accusative. It necessitates the use, however, of forms ending in a vowel for the nominative of substantives (and adjectives and pronouns). It may be remarked that -n as an accusative inflection is also found in Greek and Finnish.
The only vowels that can be employed in this connection are o and a, which, as a matter of fact, occur very frequently as the terminations of substantives and adjectives in the Slavonic languages, as well as in I. and S. Since grammatical gender, as distinct from sex, cannot be permitted in an artificial language, it is not possible to employ o and a as in natural languages, where the former is often, though not exclusively, used for the masculine (I. S., but in R. and Polish for the neuter), and the latter similarly for the feminine. One might be inclined to employ o for the male and a for the female sex, with the result that one would have no termination for inanimate things, abstract ideas, or living beings whose sex is not a matter of importance at the moment. The carrying out of this rule, however, leads to considerable difficulties which would take too long to enter into here. (This is one of the points which led to most discussion in the Delegation Committee.) As a matter of fact, a very great deal can be said in favour of the Esperanto usage of o for the substantive and a for the adjective, and, as Couturat has remarked, la bona viro is not any stranger than the Italian il buono poeta.
We need have no compunction in leaving the qualifying adjective without inflection, as is done, for instance, in English. The ending -i is very suitable for the plural of substantives, being used for this purpose in Italian, in Russian and the other Slavonic languages, as well as in modern Greek; it is also tolerably familiar to the English in foreign words, such as banditti. The only termination which might dispute the honours with -i is -s (F., although usually silent, S., E., G. partly, and Dutch), but -s cannot be used if we employ the accusative termination -n, as neither virosn nor virons could be permitted.
As regards the inflections of verbs, we are bound, if we want a termination for the infinitive, to choose, according to our fundamental principle, the -r of all the Romance languages, because neither the German -n, which we have used for other purposes, nor the palatised Slavonic -t (or -ć), can be employed, and English possesses no inflection. We require a vowel before the -r, the choice of which will be evident from what follows. For the active and passive participles we need only consider -nt and -t respectively, the vowels being also left undecided for the present. The greatest difficulty, however, is caused by the finite tenses, in which we must distinguish present, past, and future. In this respect living languages differ so much amongst themselves that the principle of maximum internationality does not suffice, especially as the inflections of tense are inextricably mixed up with those of person and number, which for our purposes are quite unnecessary. The Delegation Committee have, therefore, for the moment been unable to find anything better than the Esperanto usage of -as for the present, -is for the past, and -os for the future. The same series of vowels may also be employed for the infinitive and participles, so that the normal forms are -ar, -anta, and -ata (the final vowel a here being the adjectival termination), whilst -ir, -inta, -ita, and -or, -onta, -ota, respectively may be retained for the less frequent cases where one wishes to indicate expressly another tense in the infinitive or participle. A few à priori inflections will not cause much harm in a grammar which is so easy that it may be mastered in half an hour.
I have now arrived at the end of my investigation, in which I have endeavoured to show the method whereby the language of the Delegation has been constructed. The result is a language that everyone can easily master, and which possesses the advantage over other languages that it is based on rational scientific principles and, therefore, need not fear that some fine day it will be replaced by another and sensibly different language. Naturally improvements will be effected in details where the fundamental principles have not been sufficiently worked out, but the foundation is sound, and the common auxiliary language of mankind cannot differ very much from our "Internaciona linguo," or, to give it a shorter name, "Interlinguo," or, still shorter, "Ilo" (from the initial letters).
Otto Jespersen.
[APPENDIX]
Criticism of Esperanto
In connection with the foregoing some critical remarks on Esperanto may be made, from which one will readily perceive the reasons which made it impossible for the Délégation pour l'Adoption d'une Langue Internationale to adopt Esperanto in its present form as the international auxiliary language.
Dr. Zamenhof has given us an interesting account of the way in which his language gradually developed in his mind while he was at the Warsaw Gymnasium. Before he arrived at the conviction that the material for the vocabulary must be obtained from the Romance and Germanic languages, and that the already existing stock of international words must be used, he had "simply invented" his words, that is to say, chosen them quite arbitrarily, but with as much regard to system and brevity as possible. Although he himself noticed that such words are difficult to learn and still more difficult to remember, he has unfortunately retained in the finished language a whole series of such à priori formations, which appear in words of such frequent occurrence as who, how, where, never, everywhere, etc. The nul tempe and pro quo chosen by the Delegation agree, however, much better with the general character of language than the neniam and kial of Dr. Zamenhof.