her but are to an astonishing degree actually
convertible into each other. The upshot of such an examination would be
to feel convinced that the "part of speech" reflects not so much our
intuitive analysis of reality as our ability to compose that reality
into a variety of formal patterns. A part of speech outside of the
limitations of syntactic form is but a will o' the wisp. For this reason
no logical scheme of the parts of speech--their number, nature, and
necessary confines--is of the slightest interest to the linguist. Each
language has its own scheme. Everything depends on the formal
demarcations which it recognizes.

Yet we must not be too destructive. It is well to remember that speech
consists of a series of propositions. There must be something to talk
about and something must be said about this subject of discourse once it
is selected. This distinction is of such fundamental importance that the
vast majority of languages have emphasized it by creating some sort of
formal barrier between the two terms of the proposition. The subject of
discourse is a noun. As the most common subject of discourse is either a
person or a thing, the noun clusters about concrete concepts of that
order. As the thing predicated of a subject is generally an activity in
the widest sense of the word, a passage from one moment of existence to
another, the form which has been set aside for the business of
predicating, in other words, the verb, clusters about concepts of
activity. No language wholly fails to distinguish noun and verb, though
in particular cases the nature of the distinction may be an elusive one.
It is different with the other parts of speech. Not one of them is
imperatively required for the life of language.[91]

[Footnote 91: In Yana the noun and the verb are well distinct, though
there are certain features that they hold in common which tend to draw
them nearer to each other than we feel to be possible. But there are,
strictly speaking, no other parts of speech. The adjective is a verb. So
are the numeral, the interrogative pronoun (e.g., "to be what?"), and
certain "conjunctions" and adverbs (e.g., "to be and" and "to be not";
one says "and-past-I go," i.e., "and I went"). Adverbs and prepositions
are either nouns or merely derivative affixes in the verb.]

VI

TYPES OF LINGUISTIC STRUCTURE

So far, in dealing with linguistic form, we have been concerned only
with single words and with the relations of wo