Where there is no choice there is no Art.
Wherever a person can choose a Thought, the means whereby to express that particular Thought, and one way of several to apply the chosen means, there Art may be achieved.
The personality of a person is neither that person's nor anybody's choice, therefore it can not be considered as relevant to Art nor useful as an instrument of an Artist. It is good choosing which makes the Artist a personality, not the personality which makes a good chooser.
To propose a Thought, all that is necessary is to write it down in words and to give the script to somebody who can read and understand the chosen language.
To express a Thought (idea, feeling) by the same means, namely written words, the action of choosing words and the resultant choice of words, in addition to their meaning, must be characteristic for and related to the Thought. When a Thought is expressed so that the choice of words appears irreplaceable by a better one, during what in each period of society's history is called "all time", then the writer has written Poetry. If the reader understands the Thought not only through the meaning of words, but also through the choice of words, then the reader is reading Poetry.
There is no poetical thought but has been expressed by meaning plus choice of words. There is no Thought but can be so expressed, and there is no Art of Words but Poetry.
The choice of means plus the treatment of these means according to their particular nature plus a Thought whose nature demands expression by these means plus a definite relation between this Thought and one apparently irreplaceable selection and application of these means---these are the interdependent components of a definition of the term "ART" when the term "ART" is being used for every Human creation which has the purpose of proposing and expressing a Thought, idea, feeling, within and to Society.
The means of that particular Art called "Theater" include the Spoken Word. The spoken word expresses a Thought through the agency of the voice of a person who combines the abilities of a reader of Poetry (s.a.) with those of a speaker. A speaker apprehends the Thought not only through the meaning and the choice of words, but also through their place and pace in Time. Time is an element inseparable from the Art called Theater: in the movement of figures on the stage as well as in the "Times" implied by the Thought or Story, and also in the spoken word. Time can become a means of Art only under a certain consequent treatment.
This treatment composes a number of chosen events into a continuity of accented and non-accented moments. Events are words, tone sequences, movements, lights, etc., as well as the intervals between them. The smallest recognizable unit of Art-Time in one such continuity (a play, symphony, dance) is called "a motif". It consists of a small group of moments of which only one is accented. The number of moments and their distribution within a particular motif is called "the meter" of the motif. Every motif appears metrical in time. Language, with its greater frequency of accented moments, employs fewer different meters than does either music or movement.
The smallest group of motifs which expresses a Thought is called a sentence. If the motifs in this group are of equal meter, a metrical sentence results, as in a poem, a folkdance, almost all music up to Stravinsky, etc. If each motif in the group is of a different meter, the result is a prose sentence: of a tale, a movement, some new music since Schoenberg, etc.
Motives and sentences, quite independent of motif's meter, become larger units in Time. Thus Time becomes divided again into accented and non-accented groups of motifs and of sentences. The inner division of these larger units and the time-relations between them display for us the Form and Forms of Time: Rhythm. All sentences, metrical or prose, can be presented in all kinds of rhythm, regular or irregular. There never is "no rhythm".
When one can choose rhythm, the Artist must choose a rhythm. Only so will the nature of one's Thought become known in Time. To be able to choose, the Artist must know all the possibilities. One must know the nature of Time and Rhythm, and how it serves the interpersonal requirements of one's work. The Artist must beware of the damage which Time and Rhythm will do when used to serve the personal requirements of the Artist's own nature, following the Artist's laws instead of theirs, that is, from the Artist's inside out, that is: superficially. The Artist must know that two sentences, each sound and strong in rhythm, may appear nevertheless weak and inexpressive when following one another, and why this is so, and how it can be corrected. One will have to revise one's choice of Rhythm in each sentence for the benefit of both.
And so on, until the whole work stands and moves and speaks as one rhythmic unity, in which the varieties of motif and meter, sentence and rhythm, can be understood, remembered and related to the Thought, Idea, Feeling which the work proposes to convey.
Already existing plays of authors who were poets will have to be analyzed by the producer-regisseur with the actors. They will have to write and read the simple notation of rhythm.
The plays may be written in score already by the author, who of course would have to be a well-educated poet, composer of movement and scholar of stagecraft. And there is no law which says that a work for the theater, which always combines several arts, must be written by one author only.
Any work that is presented in Time (a play, a dance, a piece of music), but improvises on the element of Time---even though everything else may be perfect---will still be called Theater, Ballet, Music, but will not deserve the title of Art.