  The most general conception of change is simply difference or nonidentity in the features of things. Thus we speak of the change of temperature from place-to-place along a body, or the change in atmospheric pressures from place-to-place as recorded by isobars, or the change of height of the surface of the earth as recorded by a contour map. Contour lines record sameness in quantities (such as 100 metres) from the same quantity-kind (such as height), and the differences recorded by different contour lines are quantity-differences (100 metres as opposed to 200 metres). The philosophical question here is how to construe such statements of identity and nonidentity, and it seems that the problem of universals is the main issue.