 Some philosophers have sought an answer to the problem of time’s arrow by claiming that time itself is directed. They do not mean time is asymmetric in the sense intended by advocates of the tensed theory of time. Their proposals are firmly rooted in the idea that time and space are properly represented on a four-dimensional manifold. The main idea is that the asymmetries in time indicate something about the nature of time itself. Christensen (1993) argues that this is the most economical response to our problem since it posits nothing besides time as the common cause of the asymmetries, and we already believe in time. A proposal similar to Christensen’s is Weingard’s “time-ordering field” (1977). Weingard’s speculative thesis is that spacetime is temporally oriented by a “time potential”, a timelike vector field that at every spacetime point directs a vector into its future light cone. In other words, supposing our spacetime is temporally orientable, Weingard wants to actually orient it. The main virtue of this is that it provides a time sense everywhere, even in spacetimes containing closed timelike curves (so long as they’re temporally orientable). As he shows, any explication of the “earlier than” relation in terms of some other physical relation will have trouble providing a consistent description of time direction in such spacetimes. Another virtue of the idea is that it is in principle capable of explaining all the temporal asymmetries. If coupled to the various asymmetries in time, it would be the “master arrow” responsible for the arrows of interest. As Sklar (1985) notes, Weingard’s proposal makes the past-future asymmetry very much like the up-down asymmetry. As the up-down asymmetry was reduced to the existence of a gravitational potential—and not an asymmetry of space itself—so the past-future asymmetry would reduce to the time potential—and not an asymmetry of time itself. Of course, if one thinks of the gravitational metric field as part of spacetime, there is a sense in which the reduction of the up-down asymmetry really was a reduction to a spacetime asymmetry. And if the metric field is conceived as part of spacetime—which is itself a huge source of contention in philosophy of physics—it is natural to think of Weingard’s time-ordering field as also part of spacetime. Thus his proposal shares a lot in common with Christensen’s suggestion.