_To err_ = _error_; but we have no such form as _to errs_ = _errors_. Nor is it wanted. The infinitive, in a substantival sense, always conveys a general statement, so that even when singular, it has a plural power; just as _man is mortal_ = _men are mortal_. § 425. _The adjective used as a substantive._--Of these, we have examples in expressions like the _blacks of Africa_--_the bitters and sweets of life_--_all fours were put to the ground_. These are true instances of conversion, and are proved to be so by the fact of their taking a plural form. _Let the blind lead the blind_ is not an instance of conversion. The word _blind_ in both instances remains an adjective, and is shown to remain so by its being uninflected. § 426. _Uninflected parts of speech, used as substantive._--When King Richard III. says, _none of your ifs_, he uses the word _if_ as a substantive = _expressions of doubt_. So in the expression _one long now_, the word _now_ = _present time_. § 427. The convertibility of words in English is very great; and it is so because the structure of the language favours it. As few words have any peculiar signs expressive of their being particular parts of speech, interchange is easy, and conversion follows the logical association of ideas unimpeded. _The convertibility of words is in the inverse ratio to the amount of their inflection._ * * * * * CHAPTER II. SYNTAX OF SUBSTANTIVES. § 428. The phenomena of convertibility have been already explained. The remaining points connected with the syntax of substantives, are chiefly points of ellipsis. _Ellipsis of substantives._--The historical view of phrases, like _Rundell and Bridge's_, _St. Paul's_, &c., shows that this ellipsis is common to the English and the other Gothic languages. Furthermore, it shows that it is met with in languages not of the Gothic stock; and, finally, that the class of words to which it applies, is, there or thereabouts, the same generally. § 429. The following phrases are referable to a different class of relations-- 1. _Right and left_--supply _hand_. This is, probably, a real ellipsis. The words _right_ and _left_, have not yet become true substantives; inasmuch as they have no plural forms. In this respect they stand in contrast with _bitter_ and _sweet_; inasmuch as we can say _he has tasted both the bitters and sweets of life_. Nevertheless, the expression can be refined on. 2. _All fours_. _To go on all fours._ No ellipsis. The word _fours_ is a true substantive, as proved by its existence as a plural. * * * * * CHAPTER III. SYNTAX OF ADJECTIVES. § 430. _Pleonasm._--Pleonasm can take place with adjectives only in the expression of the degrees of comparison. Over and above the etymological signs of the comparative and superlative degrees, there may be used the superlative words _more_ and _most_. And this pleonasm really occurs--