2. By Agglutination.
The sentence is formed by suffixing to the word expressive of the main idea a number of others, more or less altered, expressing the relations. Examples of this are the Eskimo of North America, and the Northern Asiatic dialects.
3. By Incorporation.
The leading word of the sentence is divided, and the accessory words either included in it or attached to it with abbreviated forms, so that the whole sentence assumes the form and sound of one word.
4. By Inflection.
Each word of the sentence indicates by its own form the character and relation to the main proposition of the idea it represents. Sanscrit, Greek and Latin are familiar examples of inflected tongues.
It is possible to suppose that all four of these forms were developed from some primitive condition of utterance unknown to us, just as naturalists believe that all organic species were developed out of a homogeneous protoplasmic mass; but it is as hard to see how any one of them in its present form could pass over into another, as to understand how a radiate could change into a mollusk.
Of the four plans mentioned, Incorporation is that characteristic of, though not confined to, American tongues.
The psychological origin of this plan is explained rather curiously by Humboldt, as the result of an exaltation of the imaginative over the intellectual elements of mind. By this method, the linguistic faculty strives to present to the understanding the whole thought in the most compact form possible, thus to facilitate its comprehension; and this it does, because a thought presented in one word is more vivid and stimulating to the imagination, more individual and picturesque, than when narrated in a number of words.[[284]]
Incorporation may appear in a higher or a lower grade, but its intention is everywhere the effort to convey in one word the whole proposition. The verb, as that part of speech which especially conveys the synthetic action of the mental operation, is that which is selected as the stem of this word-sentence; all the other parts are subordinate accessories, devoid of syntactic value.