The horizontal ruler area at the top of a text window contains the expected formatting tools: you can set the paragraph containing the insertion point to be ragged-right, ragged-left, centered, or right-and-left justified; you can insert four kinds of tabs; increment or decrement line leading and paragraph leading; and, of course, slide the wrapping margins. There is also a ruler icon which, if checked, causes small ruler symbols - the Governing Rulers - to become visible to the left of some paragraphs in the text.
It appears that Paragon began by hoping to do without Word-type named paragraph styles altogether; and the curious hierarchy of ways to manipulate paragraph formatting reflects the remnants of this hope. At the bottom of the hierarchy is a mechanism for physically and namelessly manipulating paragraph styles, the Governing ruler, rather like the ruler in the original MacWrite. Under this metaphor a ruler appearing in the left margin continues to govern every subsequent paragraph until a paragraph is encountered whose format information (margins, justification, tab placement, line leading, paragraph leading, etc.) differs in some way, and then a new ruler appears in the left margin next to that differing paragraph.
You can do many things with these rulers:
(i) You can alter the format of one paragraph. <more>
(ii) You can select any number of paragraphs (contiguous or otherwise, remember) and alter their formatting. <more>
(iii) You can alter the format of one paragraph and all contiguous paragraphs governed by the same individual ruler. <more>
(iv) You can alter the format of one paragraph and all identical paragraphs - that is, all paragraphs anywhere in the document whose formatting is just like the current paragraph. This is a cool feature because you can essentially redefine a paragraph style for the whole document without ever worrying about style names. <more>
(v) You can treat the Governing rulers that appear in the margin as characters, and cut and paste them as a way of altering paragraph formats. <more>
Adam thinks that when it comes right down to using Nisus, over 90% of users will never even notice or care that they can do anything but format either the paragraph holding the insertion point or the selected paragraphs, although he admits to being fond of the ability to cut, copy, and paste ruler icons to format text. This may be true, though I happen to think that even such users will probably accidentally run across the more advanced properties of Governing rulers. But in any case we both agree that the combinations of these various actions on Governing rulers are extremely powerful, a fantastic implementation of the concept.