 Ned Markosian (1993) points out that to give a rate is to compare two different types of change. When we say that the car travels at forty mph, we are comparing one type of change—the car started off in one place and ended up forty miles distant—with another—it was one time and it is now an hour later. In that case, we can always get the rate of the second type of change by comparing back to the first. As Markosian says (ibid., 842): “If … I tell you that Montana’s passing totals increased at the rate of 21 passes per game, then I have also told you that the games progressed at the rate of one game per 21 completions by Montana.” So suppose we say that the first temporal dimension passes at a rate of one hour for every two hours of the second temporal dimension; there is no need to invoke a third temporal dimension in order to state the rate at which the second passes, for we have already given that rate: an hour of the second temporal dimension passes for every half hour of the first. Indeed, as Markosian points out, we need not even invoke a second temporal dimension, for any time we give a rate of any ordinary process with respect to time—such as that the Earth goes around the sun once every year—we have thereby stated the rate at which time passes with respect to those ordinary processes: time passes at the rate of one year for every orbit of the Earth around the sun.