Just as we can verbify the idea of a quality in such cases as “reddens,” so we can represent a quality or an action to ourselves as a thing.  We speak of “the height of a building” or “the fall of an apple” quite as though these ideas were parallel to “the roof of a building” or “the skin of an apple,” forgetting that the nouns (height, fall) have not ceased to indicate a quality and an act when we have made them speak with the accent of mere objects.  And just as there are languages that make verbs of the great mass of adjectives, so there are others that make nouns of them.  In Chinook, as we have seen, “the big table” is “the-table its-bigness”; in Tibetan the same idea may be expressed by “the table of bigness,” very much as we may say “a man of wealth” instead of “a rich man.”

But are there not certain ideas that it is impossible to render except by way of such and such parts of speech?  What can be done with the “to” of “he came to the house”?  Well, we can say “he reached the house” and dodge the preposition altogether, giving the verb a nuance that absorbs the idea of local relation carried by the “to.”  But let us insist on giving independence to this idea of local relation.  Must we not then hold to the preposition?  No, we can make a noun of it.  We can say something like “he reached the proximity of the house” or “he reached the house-locality.”  Instead of saying “he looked into the glass” we may say “he scrutinized the glass-interior.”  Such expressions are stilted in English because they do not easily fit into our formal grooves, but in language after language we find that local relations are expressed in just this way.  The local relation is nominalized.  And so we might go on examining the various parts of speech and showing how they not merely grade into each other 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,