A Temporal Mereology for Distinguishing between Integral Objects and Portions of Stuff

We develop a formal theory of mereology that includes relations that change over time. We show how this theory formalizes reasoning over domains of material objects, which include not only integral objects (my computer, your liver) but also portions of stuff (the water in your glass, the blood in a vial). In particular, we use different mereological summation relations to distinguish between the ways in which i) integral objects, ii) portions of unstructured, homogenous stuffs (e.g. the water in your glass), and iii) mixtures (the blood in a vial) are linked to their parts over time.