We often speak poetically of the ‘flow’ of ‘the river of time’. This is clearly wrong, because rivers, unlike the water in them, do not flow – otherwise maps would be continually out of date, with all rivers disappearing into the ocean. But couldn’t time move like the water in the river? Let’s leave aside the question – not as daft as may seem – of whether ‘water’ here means all the water in the river or the water at a specific place, and focus on the more obvious problems. If time flows, what does it flow in? Stuff such as water flows in space, relative to other stuff in space (such as banks) that flow not at all, or more slowly. This is clearly not something that time could manage: time could not flow in or relative to time in the way that spatially-extended, located matter such as water flows between other bits of spatially-extended matter. Besides, how quickly would it flow? The obvious answer, one second per second, demonstrates the vacuity of the very notion of ‘time on the move’. Velocity or rate cannot have the same dimension on both the numerator and the denominator. Nevertheless, the idea of temporal flow is irresistible. It gets a bit of a boost from the way the calendar makes us think of time in lumps. On Friday at noon, my doctor’s appointment next Wednesday noon is five days away. On Saturday at noon, Wednesday noon will be four only days away. Wednesday, it seems, is coming nearer, bearing the dreaded appointment in its belly.
more from Raymond Tallis at Philosophy Now here.