  One's answers to these questions depends on one's views on the nature of persistence through time and change. Broadly speaking, there are two realist views of change: Perdurantism (or four-dimensionalism or the doctrine of temporal parts), which reduces persisting objects to more fundamental, momentary objects, and endurantism (or three-dimensionalism), which takes persisting objects as primitive, maintaining that a persisting object is “wholly present” at each time it exists (see Crisp and Smith 2005 for an interesting attempt to articulate this notion). Proponents of the perdurantism include Armstrong 1980, Heller 1990, Jubien 1993, Lewis 1971,  1976, 1986, and 1988, Quine 1960 and 1963, Robinson 1982, Russell 1927, Smart 1955 and 1972, Taylor 1955, and Williams 1951, among others. Versions of endurantism are defended in Chisholm 1976, Forbes 1987, Geach 1966 and 1967, Haslanger 1985, 1989a/b, and 2003, Hinchliff 1988 and 1996, Johnston 1983 and 1987, Lowe 1987, 1988, and 1998, Mellor 1981 and 1998, Thomson 1983, van Inwagen 1990 and 2000, Wiggins 1968, 1980, and 2001, and Zimmerman 1996 and 1998a/b, among others. (There are important differences between the versions of endurantism defended in these works, related to whether or not “tense is taken seriously”, presentism is accepted or rejected, whether or not seemingly monadic properties like being age 64 are treated as relations between individuals and times, and whether or not the instantiation relation between individuals and properties is claimed to obtain only relative to a time. See the entries identity over time and temporal parts for further discussion.)