 In contrast to his theories of place and general space, Wolff holds a much more realistic theory of time. In a strict sense, place and space serve an explanatory role for Wolff at two distinct levels of description (viz. the micro-physical level and the level of appearance). Since atomic elements are unextended, the concepts of place and space are considered by Wolff to be extraneous at the atomic level. Time, however, is not. Atomic elements are in time insofar as each element is in a constant state of change. In his most general description of time, Wolff writes: “[t]ime is the order of successive things in a continuous series” (Ont. §572). Since each atomic element produces in-itself a constant and continuous series of changes, time is regarded by Wolff as the objective measure of such changes. One clear statement of the Wolffian view of the relationship between time and change can be found in a letter to Kant (dated 13 October 1770) from Johann Heinrich Lambert. Lambert (1728–77) writes: