 Such accounts, as we have noted above, seem to support the Aristotelian solution. But they are not the only accounts. On some accounts there is no such fundamental ontological difference between the future and the present and past; the impossibility of affecting the past lies not in the fact that the passage of time puts a constraint on what can be caused, but rather in the fact that it is the direction of causation which determines the direction of time (Swinburne 1994, Mellor 1981 and 1998). On yet other accounts the impossibility is simply a fundamental metaphysical fact which is not open to further analysis or explanation.