On the one hand, text is composed of a hierarchy of lexical units:

    * characters
    * words
    * phrases
    * sentences
    * paragraphs
    * subsections
    * sections
    * chapters
    * documents 

These units reflect the meaning of the text. When the user is thinking in terms of meaning, the editor should provide an editing model -- and commands -- that reflect these units. Since text is read sequentially, the one-dimensional model is well-matched to this mode.

On the other hand, the printed page is composed of:

    * characters, which are arranged into
    * words, which are arranged into
    * lines, which are arranged into
    * pages, which are arranged into
    * documents