Visual rhetoric is "the ability of the writer to achieve the purpose of a document through visual communication" ("Visual Rhetoric" 77). The success of visual rhetoric depends upon the extent to which a document's visual elements consider audience, purpose, and context. For example, if a document intended for elderly readers uses 8-point type, audience has not been properly considered and the document's visual rhetoric fails at the intra-textuallevel. If a textbook uses only one degree of heading but attempts to present a hierarchy of information, purpose has not been considered and the document's visual rhetoric fails at the inter-textual level. If an annual report includes minute details in graphs intended to show general trends, purpose has not been considered and the document fails at the extra-textual level. If a field guide intended to be carried in a scientist's pocket is sixteen inches wide and twenty-four inches tall, context has not been considered and the document's visual rhetoric fails at the supra-textual level.