In all sentences containing the statement of a reciprocal or mutual action there are in reality two assertions, viz. the assertion that A strikes (or loves) B, and the assertion that B strikes (or loves) A; the action forming one, the reaction another. Hence, if the expression exactly coincided with the fact signified, there would always be two propositions. This, however, is not the habit of language. Hence arises a more compendious form of expression, giving origin to an ellipsis of a peculiar kind. Phrases like Eteocles and Polynices killed each other are elliptical for Eteocles and Polynices killed—each the other. Here the second proposition expands and explains the first, whilst the first supplies the verb to the second. Each, however, is elliptic. The first is without the object, the second without the verb. That the verb must be in the plural (or dual) number, that one of the nouns must be in the nominative case, and that the other must be objective, is self-evident from the structure of the sentence; such being the conditions of the expression of the idea. An aposiopesis takes place after a plural verb, and then there follows a clause wherein the verb is supplied from what went before.
When words equivalent to each other coalesce, and become compound; it is evident that the composition is of a very peculiar kind. Less, however, for these matters than for its value in elucidating the origin of certain deponent verbs does the expression of reciprocal action merit the notice of the philologist. In the latter part of the paper it will appear that for one branch of languages, at least, there is satisfactory evidence of a reflective form having become reciprocal, and of a reciprocal form having become deponent; this latter word being the term for those verbs whereof the meaning is active, and the form passive.
Beginning with those methods of denoting mutual action where the expression is the least explicit and unequivocal, it appears that in certain languages the reciprocal character of the verb is implied rather than expressed. Each man looked at his brother—or some equivalent clause, is the general phraseology of the Semitic languages.
More explicit than this is the use of a single pronoun (personal, possessive, or reflective) and of some adverb equivalent to the words mutually, interchangeably, &c. This is the habit of the Latin language,—Eteocles et Polynices invicem se trucidaverunt: also of the French, although not invariably, e. g. s'entr'aimer, s'entredire, s'entrebattre: also of the Mœso-Gothic—galeikái sind barnam tháim vôpjandam seina missô =[a] ὁόμοιοί ἐισι παιδίοις τοῖς προσφωνοῦσιν ἁλλήλοις] = loquentibus ad invicem.—Luc. vii. 32. Deutsche Grammatik, iv. 322, and iii. 13. The Welsh expressions are of this kind; the only difference being that the adverb coalesces with the verb, as an inseparable particle, and so forms a compound. These particles are dym, cym, or cy and ym. The former is compounded of dy, signifying iteration, and ym denoting mutual action; the latter is the Latin cum. Hence the reciprocal power of these particles is secondary: e. g. dymborthi, to aid mutually; dymddadlu, to dispute; dymgaru, to love one another; dymgoddi, to vex one another; dymgredu, to trust one another, or confide; dymguraw, to strike one another, or fight; çyçwennys, to desire mutually; cydadnabod, to know one another; cydaddawiad, to promise mutually; cydwystlaw, to pledge; cydymadrawn, to converse; cydymdaith, to accompany; ymadroddi, to discourse; ymaddaw, to promise; ymavael, to struggle; ymdaeru, to dispute, &c.
The form, which is at once current, full, and unequivocal, is the one that occurs in our own, and in the generality of languages. Herein there are two nouns (generally pronouns), and the construction is of the kind exhibited above—[a]ἁλλήλους], each other, einander, l'un l'autre, &c.
Sometimes the two nouns remain separate, each preserving its independent form. This is the case in most of the languages derived from the Latin, in several of the Slavonic and Lithuanic dialects, and in (amongst others) the Old Norse, the Swedish, and the Danish,—l'un l'autre, French; uno otro, Span.; geden druheho, Bohemian; ieden drugiego, Polish; wiens wienâ, Lith.; weens ohtru, Lettish; hvert annan (masc.), hvert annat (neut.) Old Norse. See D. G. iii. 84.
Sometimes the two nouns coalesce, and form words to which it would be a mere refinement to deny the name of compounds: this is the case with the Greek—[a]ἁλλήλον], [a]ἁλλήλοις], [a]ἁλλήλους].
Sometimes it is doubtful whether the phrase consist of a compound word or a pair of words. This occurs where, from the want of inflection, the form of the first word is the same in composition as it would have been out of it. Such is the case with our own language: each-other, one-another.
Throughout the mass of languages in general the details of the expression in question coincide; both subject and object are almost always expressed by pronouns, and these pronouns are much the same throughout. One, or some word equivalent, generally denotes the subject. Other, or some word equivalent, generally denotes the object, e. g. they struck one another. The varieties of expression may be collected from the following sketch:—
1. a. The subject is expressed by one, or some word equivalent, in most of the languages derived from the Latin, in several of the Slavonic dialects, in Lithuanic and Lettish, in Armenian, in German, in English, and doubtlessly in many other languages—l'un l'autre, Fr.; uno otro, Sp.; ieden drugiego, Polish; wiens wienâ, Lith.; weens ohtru, Lett.; me mæants, Armenian; einander, Germ.; one another, Engl.