Tuesday, 1 May 2012

The supposed passage of time

Time seems to pass - at least, that’s what plenty of people (some philosophers included) seem to think. However, on reflection, it’s pretty baffling what this claim is supposed to amount to. Taking it literally, we might suppose that time flows literally like a river, with moments passing by like water passing from one section of the river to the next.
'The Persistence of Memory' by Salvador Dali
However, if this is the way in which time flows, it makes sense to ask the question ‘how fast does time flow?’ The problem is, we cannot answer this question without talking nonsense. A river, let’s say, flows at x cubic liters per second - there’s nothing problematic about this observation. In the case of time, the only answer we can give to the question is ‘one second per second.’ But this is not a proper rate at all - it doesn’t tell us anything about the rate of time’s flow, since it is trivially true. It reduces to 1/1, which is not a rate; it’s just ‘1’. We are none the wiser.

We should therefore look to describe the passage of time in some other, perhaps metaphorical, sense. But to do this, we need to get a grip of what exactly we mean by the claim that ‘time passes.‘ Talk of events zooming out of the future, past us through the present, and into the past is all well and good, but seems pretty vague when considered in any depth. We see objects moving about, changing position - and ‘watching the world go by’ just means watching lots of these objects move about. But that this should indicate a great sweeping movement of all spatial events into the past seems unclear. 

Everyday talk about time’s passage seems puzzling from a philosophical perspective because the notion seems so ill-defined. However, we still think it’s true to say that ‘world war two happened’, and that ‘Fidel Castro will die’ (eventually). Descriptions of past and future events seem to require the passage of time, for what else could it mean for an event to become past if not to recede into the past, replaced by a moment that was once future?

There’s a strong case for arguing that time does not flow at all - that events are just laid out in a big static block, called ‘space-time.’ On this view, time is just like space - one dimension of this four-dimensional block of reality. If the universe is ‘static’ in this way (and most physicists already think that it is), then there is no reason to suppose a passage of time exists at all. Rather, time’s passage is a subjective illusion in our consciousness. A good analogy is one of a reel of film, which though giving the illusion of real motion, is just a series of still images all following each other. Life is similarly a series of stages, ‘sped up’ to look like passage in the minds of conscious observers. 
The proponent of this view, which I think is probably true, must give an account of what it means to say that time passes. Various theories have been proposed concerning the inner workings of the human mind, and how it might produce a sensation of passage, which does not exist in reality. However, for me, the biggest conceptual task in thinking about this view is the notion that time is like space. As noted, this is uncontroversial in physics, but radical in everyday talk about the world. It takes a bit of getting one’s head around. Still; think about what it means to say that 'time passes'; and if, like me, you are puzzled by the notion, then a static universe without real passage starts to make much more sense.
(More posts to follow on this view, sometimes loosely labelled ‘The B-theory’, or ‘four-dimensionalism.’)

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