 The motivations for temporalism are both metaphysical and semantic. On the metaphysical side, A-theorists about time (see the entry on  time)  think that corresponding to predicates like “is a child” are A-series properties which a thing can have at one time, and lack at another time. (Hence, on this view, the property corresponding to “is a child” is not a property like being a child in 2014, since that is a property which a thing has permanently if at all, and hence is a B-series rather than A-series property.) But then it looks like the proposition expressed by “Violet is a child”—which predicates this A-series property of Violet—should have different truth-values with respect to different times. And this is enough to motivate the view that we should have an index for a time.