I propose that human experience of matter provides the source domain for the metaphor that motivates the grammatical category of aspect in Russian. This model is a version of the universal TIME IS SPACE metaphor, according to which SITUATIONS ARE MATERIAL ENTITIES, and, more specifically, PERFECTIVE IS A DISCRETE SOLID OBJECT versus IMPERFECTIVE IS A FLUID SUBSTANCE. The contrast of discrete solid objects with fluid substances reveals a rich array of over a dozen properties; the isomorphism observed between those properties (...) and the complex uses of aspect in Russian is compelling. This model presents a more finely articulated account of Russian aspect than feature analysis can achieve. Although some of these properties overlap significantly with the count versus mass distinction often associated with aspect, the properties provide more detail and ground the metaphor to concrete experience. Properties of matter can be divided into three groups: inherent properties such as edges, shape, and integrity (which correspond to inherent situation aspect); interactional properties such as juxtaposition, dynamism, and salience (which correspond to discourse phenomena of aspect); and human interactional properties such as graspability and impact (which correspond to pragmatic phenomena of aspect). The interactional and human interactional properties can be used to motivate subjective construal, whereas the inherent properties serve as default motivators. The model will be demonstrated in detail using Russian data, followed by a survey comparing Russian with the other Slavic languages, which will show that deviations consist of either non-implementation of a given property, or the implementation of an inherent (default) property in place of an interactional or human interactional property. This model will be contrasted with a brief discussion of a selection of non-Slavic languages. The specific metaphor in this model does not apply beyond Slavic, but perhaps it will encourage investigation into the source domain of aspect in other languages. There appears to be a correlation between the relatively heavy morphological investment Slavic languages make in nominal individuation and the individuation of situations presented in this metaphorical model. (shrink)