 Whatever can be predicated of a Leibnizian substance is either an attribute (a permanent and common characteristic (GP ii, 227, 257ff)), sometimes called “property” (GP ii, 258/L 533), or an accident (a transitory and individual characteristic (GP ii, 458/L 605; GP iv, 363)), sometimes called “modification” (G ii, 258/L 533; GP ii, 503f). In contemporary lingo, we would call an attribute a “property” and accident a “property-instance” or “trope.” Action is an attribute of substance, for Leibniz defines substance as “a being capable of action” (GP vi, 598). A perception is an accident of a substance, for the action of a substance consists precisely in the fact that they are always changing their perceptions. Now, an attribute must not be considered a substance, since it would be a mistake to equate action with what is acting, or extension with what is extended (New Essays A vi, 6, 210f). Neither is an attribute to be considered an accident, for “an attribute may be predicated of several substances at the same or at different times while an accident can never inhere in more than one substance at the same or at different times” (Clatterbaugh, 1978, 3).