It is well known that adjectives describing persons can be used as nouns. The poor are always with us.  The rich live in their own world.  Honour the mighty and the brave. In this use the phrase the+Adj, can have all the syntactic properties of a noun. It can be the subject of a sentence (see the above examples), the object (The rich despise the poor) object of a preposition (Politicians always swear by the poor) and the complement (God’s children are the poor).

But the headword in this structure, the adjective, shows none of the morphological features of a noun.  It cannot inflect for number.  The poor is understood as standing for the whole class of poor people and is necessarily plural in meaning. So any referring pronoun in the sentence has to be in the plural, not singular. The poor bemoan their lot. (Not: his lot.) And agreement is with a plural verb.  The poor are (not is) always with us. Finally, the headword cannot take the possessive form: the problems of the poor; not: the poor’s problems.

These restrictions on adjectives used as nouns are not always understood. Here is a citation.  In America the rich must drive his own car as the poor does - DH.  Nov. 30, 2002, edit page. Look at the referring pronoun his. How can this singular pronoun refer to the rich which is generic in sense and hence, necessarily, plural? Agreement, in the second clause fails for the same reason. The required form of the verb is do not does (as the poor do). The correct form of the sentence is; In America the rich must drive their own cars as the poor do. 

And now for an example of an impermissible possessive: the poor’s perception of the problem It should be clear by now that adjectives which can be used as nouns referring to persons have one fixed structure: the +Adj, which admits of no variation or change. The article has to be the, not a or zero:  *a poor languishes/ *poor languish  - are both out. The article the cannot be replaced by any of the indefinite pronouns — all. both, some. none, each, etc. *some poor have made a representation to the Chief Minister /* No poor will be ignored.

Similar remarks apply to indefinite pronouns. These can be used to modify a noun (some boys, a few girls).  This use is called attributive. They can also be used by themselves.  All are welcome. Some are wise; some otherwise. Many are called but few are chosen.  This use is called substantive.  In the substantive use they function like nouns.  They can appear as the subject or object or the complement in a sentence. But, as with adjectives functioning like nouns, they show no change in form. It is of course obvious that a word like some has no singular form or that each has no plural form. What needs to be pointed out is that they cannot take a possessive form either. Ramesh and his sister have considerable real estate. They appointed an agent to manage both’s.  This may look pretty absurd and unlikely.  But here is a citation. Vince Mc Mohan (World Wrestling Entertainment owner) and Donald Trump will have on Sunday a wrestler compete on each’s behalf in the ‘Battle of the Millionnaires’ at Wrestle Mania 23 in Detroit.  The loser will have to have his head shaven — San Jose Mercury news, March 29, 2007, p. A 17.

The one exception is one.  This has several uses. In one use it refers to persons and in this use it can have a possessive form. One should mind one’s business. One can combine with the indefinite pronouns each, every, no, to form the compound indefinite pronouns someone, everyone, no one.  These forms, too, can appear in the possessive.  Someone’s, fault/ everybody’s business is nobody’s business.

Another kind of exceptional behaviour is seen in all. This can be singular or plural depending on whether reference is to persons / things or to some thing vague and general.  In the former case it is always construed as plural and takes a plural verb.  All are welcome.  In the latter it is singular, All’s well that ends well (All is well…)
The indefinite pronoun none, too, is exceptional.  It can be construed as singular or plural.

We can now state a parallelism between adjectives used as nouns and the substantive use of indefinite pronouns. The the+Adj. phrase is always generic in meaning and plural in reference. The indefinite pronouns used substantively can have generic or specific reference but are invariant in number (with the exception of one and all). Agreement can be with a singular or plural verb depending on the indefinite pronoun (exceptions: one, all).What is common to both is: they don’t have a possessive form (barring one and the compound forms)

The writer can be contacted at ksyadurajan@yahoo.com