 If we were providing the metaphysical grounds of rates of change, Smart might be right that this would lead to a vicious regress, since arguably grounding is asymmetric (see e.g., Rosen 2010,  115).[15]  If the car travels at the speed it does in virtue of something to do with the passage of time then, arguably, time cannot pass at the rate it does in virtue of anything to do with the speed of the car, and so we need to appeal to the passage of a second temporal dimension to provide the ontological grounds of the rate of passage of the first. If the passage of this second temporal dimension grounds facts about the passage of the first temporal dimension, it itself cannot pass in virtue of facts concerning the passage of the first, and so we need to appeal to a third temporal dimension, and so on. And even if we hold that it’s possible for there to be infinitely descending chains of grounds, it seems absurd in this case to suppose that there are in fact infinitely many temporal dimensions. But that is not what is going on. When we explain the speed of the car by appeal to the passage of time, we’re not providing the ontological grounds of its speed, we’re simply showing a connection between two things: the movement of the car and the passage of time. Likewise for the rate of time’s passage itself: we are not seeking to provide the ontological grounds of time’s passage in stating its rate, for the ontological grounds are plausibly just the nature of time itself. Rather, when we compare the two changes, we are simply trying to illuminate one or both of those changes by pointing to the way they relate. That is the only sense in which one explains the rate of one change when comparing it to another kind of change: the mutual connection tells us something enlightening about each. It is not to give a metaphysical explanation in the sense of providing the metaphysical grounds of either rate of change. Compare: if I tell you that the value of a US dollar is 0.7 British pounds (and therefore that the value of a British pound is 1.43 US dollars), this is not to say that the US dollar has the worth that it has in virtue of standing in this relation to the British pound. The US dollar relates thus to the British pound because of what they are each worth; they are not worth what they are in virtue of standing in that relationship. What makes it the case that the US dollar is worth what it is is some incredibly complex set of facts concerning economics, monetary policy, etc. To give an exchange rate is not to give the grounds of the value of the currencies, but merely to say something substantive about each value by stating their connections. Likewise with rates of change, which is why Markosian is able to resist Smart’s regress in this manner. Coherentist explanations might be controversial when it comes to providing ontological grounds, but they are less so when it comes to simply casting light on the nature of some phenomena by showing how they connect. So whether a regress argument even gets going will depend on the explanatory ambitions of the view being targeted.