as happening in the future.  A language can tolerate only a certain number of ambiguities arising from words of the same sound having different significations, and therefore the extent to which a language has utilized some phonetic distinction to keep words apart, has some influence in determining the direction of its sound-changes.  In French, and still more in English, it is easy to enumerate long lists of pairs of words differing from each other only by the presence or absence of voice in the last sound; therefore final b and p, d and t, g and k, are kept rigidly apart; in German, on the other hand, there are very few such pairs, and thus nothing counterbalances the natural tendency to unvoice final consonants.’

[Footnote 12:  A Modern English Grammar on Historical Principles, by Otto Jespersen, Heidelberg, 1909.  Streitberg’s Germanische Bibliothek, vol. i, p. 441.]

3. That homophones are self-destructive and tend to become obsolete.

For the contrary contention, namely, that homophones do not destroy themselves, there is prima facie evidence in the long list of survivors, and in the fact that a vast number of words which have not this disadvantage are equally gone out of use.

[Sidenote:  Causes of obsolescence.]

Words fall out of use for other reasons than homophony, therefore one cannot in any one case assume that ambiguity of meaning was the active cause:  indeed the mere familiarity of the sound might prolong a word’s life; and homophones are themselves frequently made just in this way, for uneducated speakers will more readily adapt a familiar sound to a new meaning (as when my gardener called his Pomeranian dog a Panorama) than take the trouble to observe and preserve the differentiation of a new sound.  There is no rule except that any loss of distinction may be a first step towards total loss.[13]

[Footnote 13:  To give an example of this.  In old Greek we and you were [Greek:  aemeis] and [Greek:  umeis]:  and those words became absolutely homophonous, so that one of them had to go.  The first person naturally held on to its private property, and it invented sets for outsiders.  Now the first step towards this absurdest of all homophonies, the identity of meum and tuum, was no doubt the modification of the true full u to ii.  The ultimate convenience of the result may in itself be applauded; but it is inconceivable that modern Greek should ever compensate itself for its inevitable estrangement from its ancient glories.]

It is probable that the working machinery of an average man’s brain sets a practical limit to his convenient workable vocabulary; that is to say, a man who can easily command the spontaneous use of a certain number of words cannot much increase it without effort.  If that is so, then, as he learns new words, there will be a tendency, if not a necessity, for him to lose hold of a corresponding number of his old words; and the words that will first drop out will be those with which he had hitherto been uncomfortable; and among those words will be the words of ambiguous meaning.