Nominative/absolutive case and verb agreement are, in many languages, indicators of a category which is here called VIEWPOINT: the perspective from which the speaker describes the event. The order of NP constituents in a sentence encodes ATTENTION FLOW, which is the order in which the speaker expects the hearer to attend to them. Split ergative case-marking patterns are shown to reflect conflicts between the most natural viewpoint and attention-flow assignments. It is argued that the characterization and grammatical marking of an event as first-hand or inferred knowledge for a speaker, and as intentional or inadvertent for an actor, can be described in terms of whether the entire event or only its terminal phase is directly accessible to the conscious mind of the speaker and the actor, respectively; and that these categories can also be described in terms of attention flow and viewpoint.