A classification of propositions (consisting of a verb and its arguments) is presented with a stipulation of the properties of each type, and clarification is given for how the classfication and the properties function in the interaction between propositions and Japanese aspectual auxiliary verbs. The different types of verbs include: (1) state types (indicating state of being); (2) activity types (specifying a particular ongoing action); (3) accomplishment types (identifying an activity toward a particular object or concept); (4) achievement types (indicating the completion of an action); (5) plural completion types (indicating completion of an event that was performed more than once); and (6) plural activity types (indicating that an activity was performed more than once). The propositions and properties of each verb type are discussed in the context of the Japanese verb "ir-" in the following areas: general rules for the auxiliary verb "ir-"; aspect of state resulting from action; aspect of experience; aspect of iterative event, and aspect of ongoing event. (DJD)