Abstract
This paper is an attempt to show theoretically the possible range of sentence structures of languages. The author's principle is that this problem can be solved if we approach it, first, from the viewpoint that language must reflect the ways of being of the real world so as to be able to be useful as a way of communication and, second, from the viewpoint that language must be so systematic that it can be learn and spoken by every one in the language-speaking society.
The first property of language determines the possible range of the sentence structures. The second not only determines this range in its own way but also makes the language choose one or a few from many possible structures.
The author shows some fundamental theoretically deduced results which seem to him universal or almost universal.
