The Middle Voice becomes, by an elision, the Neuter Verb. I walk, means, I walk myself. Neuter Verbs fall, then, into the Category of Reciprocal Action.
The Typical Neuter Verb, the Typical Verb, in fine, of all verbs, is the Substantive or Copula Verb to be, the Verb of Existence or Being.
I am, means, I am myself, or, I keep or hold myself in being.
In strictness, the verb to be is the only Verb. Every other Verb is capable of Solution into this one, accompanied by a Participle; thus,
I walk, becomes, I am walking, etc.
By this analysis, the Verb, as such, falls back among words of Relation, or mere Connectives. It may then be classed with Prepositions and Conjunctions; its office of Connection being still peculiar, however, namely, to intervene between the Subject and the Predicate. Participles, into which all other verbs than this Copula, are so resolved, then fall back in like manner into the Class of Adjectives. The Tempic and Motic Word-Kingdom is thus carried back to its dependence upon the Spacic and Static Word-Kingdom, as basis; in the same manner as, in Nature, Time and Motion have Space and Rest for their perpetual background.
Reduced to this degree of simplicity, there are but three Parts of Speech: 1. Substantives; 2. Attributes; and 3. Words of Relation; which correspond with 1. Things; 2. Properties of Things; and 3. The Interrelationship of Things, of Properties, and of Things and their Properties, in the Universe at large.
The Adverb has not been mentioned. Analysis reduces it in every instance to an Oblique Case of the Substantive, or, what is the same thing, to a Substantive governed by a Preposition; and hence, by a second transfer, as shown above, to the class of Adjectives of Relation: thus, happily means in a happy manner; now means in the present time, etc.
In the Grammatical Motismus the Three Tenses,—for there are but three strictly, or in the first great natural Division of Time,—namely, the Past, the Present, and the Future, correspond with the Grand Three-fold Division of The Tempismus, the Universal Ongoing or Procession of Events, the Grandis Ordo Naturæ; namely, the Past, the Present, and the Future, as the Three-fold Aspect of Time and of the Universe of Res Gestæ, or Things Done, and Contained in Time, as distinguished from the other equal Aspect of the total Universe, namely, the Static Expansion of the Universe in Space.
Mode, which is subsequently developed in Music as a Distinct Grouping of Categories, finds here, in the domain of Relation, a subordinate development, in connection with the Verb.
Kant's Subdivision of Mode, as a group of Categories is, 1. Possibility and Impossibility; 2. Being and Not-Being; and 3. Necessity and Accidence.
It is obvious that Possibility is that Category which is expressed grammatically by the Potential Mode (from potentia, power, possibility); otherwise called the Conditional Mode. I should do so and so if—The Negative Form of this Mode expresses Impossibility: I should or could not do so and so unless, etc.