McTaggart's Paradox: An Unseen Challenge to Presentism — Epoche B2
What McTaggart's Argument Costs the Presentist McTaggart's argument for the unreality of time is usually presented as a threat to the A-theory in general [1] , and presentism is usually presented as the A-theory's most robust form. Both descriptions are misleading, and correcting them changes the score. Presentism has the cleanest escape from McTaggart's regress of any A-theory. The escape works. What this column argues is that it works by removing the thing McTaggart's argument was about, and that a presentist who takes it can no longer say what motivated the A-theory in the first place: that time passes. This is a claim presentists deny, and A. N. Prior denied it in advance [2] . His reply is set out below and answered. Two ways of ordering events In 'The Unreality of Time' (1908) McTaggart distinguishes two orderings of the positions in time. Under the first, positions are ordered as earlier and later: the Battle of Hastings is earlier than the Great Fire, and that never alters. He calls this the B-series. Under the second, positions are past, present or future [3] : the Great Fire is past [4] , this sentence is present, next winter is future. He calls this the A-series, and A-determinations, unlike B-relations, do alter. Next winter will become present and then past. McTaggart's first claim is that the A-series is essential to time. The B-relations never change, so if the B-series were all there were, nothing would ever be different from how it was, and there would be no change. His second claim is that the A-series is contradictory. Time then requires something impossible, and so is unreal. The regress The contradiction is easy to state. Past, present and future are incompatible: no event has more than one of them. Yet every event has all three. The Great Fire is past, was present, and was future. The obvious reply is that it does not have them at once. It is past now, was present in 1666, and was future before that. McTaggart's response to the reply is the argument's whole force. Those qualifications are themselves tensed. To say the fire was present is to say that there is a moment at which its presentness holds, and that moment is itself past. So the moment now bears an A-determination, and it bears the other two as well, for the same reason the fire did. Repairing the contradiction at one level reproduces it at the next, and no level is ever reached at which the repair is complete. What makes the regress bite The regress needs a premise that is easy to miss. It needs pastness, presentness and futurity to be properties, and it needs there to be things — events, moments — that bear them. Only then can one thing be found bearing three incompatible ones. McTaggart's A-series is a series: a domain of positions, ordered by which determinations they carry. That premise is what a presentist rejects. The presentist escape Presentism is the view that only present things exist. There is no Great Fire, now, to bear the property of pastness, and no future winter to bear futurity. There is what is happening, and nothing else. The presentist therefore does not analyse 'the fire is past' as ascribing a property to the fire. He treats it as a whole sentence governed by an operator: it was the case that the fire is occurring. Prior built a formal logic for these operators, in which tenses attach to sentences and not to things. The regress cannot start. To get it going McTaggart must find an item carrying two incompatible determinations, and on this view no item carries any determination whatever, because there are no non-present items and the present ones are simply what is. The tensed sentences are true or false; nothing has properties it also lacks. This is the best answer any A-theorist has to McTaggart, and it is not usually credited as such. It is not a patch. It removes the subject matter of the argument. What the escape costs Removing the subject matter has a consequence. McTaggart's A-series was doing a job. It was what made change possible: positions successively acquire presentness and lose it, and that acquiring and losing is the passage of time. Ask what corresponds to this on presentism. Nothing acquires presentness, because the only things there are are present and were never anything else. Nothing loses it, because when a thing ceases to be present it does not exist to have lost anything. There is no succession of states, since there is only ever one state. What there is, is a set of sentences whose truth-values differ depending on when they are uttered. That is a thinner thing than passage, and it is thinner in the exact respect that mattered. McTaggart argued that the B-series alone cannot give us change because its relations never alter. The presentist's position has no altering relations either. It has one moment and a stock of operators. A different answer to the same worry It is worth setting beside this a treatment that goes the other way. Sengzhao [5] , a disciple of Kumārajīva working in Chang'an around the year 400, opens the Zhaolun with a treatise usually rendered 'Things Do Not Shift'. His question is why we believe that things move through time, and his answer is that we are misreading our own evidence. We judge that a thing has moved from the past into the present because we do not find the past thing here now. Sengzhao accepts the observation and rejects the inference. The past thing is not here because it is there, in the past, where it remains; the present thing is here, in the present, where it remains. Each is confined to its own time and neither travels. What we took to be evidence of passage is evidence that things do not pass. The argument is put to a Buddhist purpose about the emptiness of what appears to change, and later Chinese Buddhists disputed the treatise vigorously; nothing here depends on its wider conclusions. What it supplies is the observation that a thing's being confined to its own time can be read as a reason for denying passage rather than fo