the time travel illusion

It's been an interesting week for time travel. For those of you who have been cavorting around in the 26th Century, let me fill you in. First, there was an article saying that time travel is impossible. Then only days later, another article from a different venue virtually telling us to get our advance TARDIS bookings.
From sfgate.com comes a quote from time researcher David Miller:

"If you have the block universe view, the future and the past are not any different, so there's no reason why you can't have causes from the future just as you have causes from the past," says David Miller of the Centre for Time at the University of Sydney in Australia.

The 'block universe', by the way, is a reference to Einstein's theory that time is simply another dimension, the fourth dimension, in the space time continuum. Therefore, time unfolding is an illusion, because we are simply traveling a path through a static space-time "space".
But the nay-sayers have a different view. Over at Livescience, Charles Liu of the City University of New York (CUNY), says time travel is impossible">time travel is impossible.

Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom.
"In this four-dimensional space-time, you’re only able to move forward in time," Liu told LiveScience.

So which is it?
One argument against time travel is the existence of multiple paradoxes, explored at length in science fiction. For example, imagine you go back in time and change the past. For example, you stop World War I from happening. Okay, then wouldn't World War I already have stopped? Even if time travel is invented in 300 years from now and someone goes back and prevents World War I from ever occuring, why are we living in a universe where it happened? The standard scifi explanation for this is the creation of multiple timelines, one where it happened and one where it didn't, but that seems like a cop-out that creates more problems than it solves. For example, what if multiple time travelers from multiple timelines travel back and erase each other's timelines? The problems multiply to absurdity, and it is exactly these absurd paradoxical tangles that lead many to blow the whistle.
While time-travel paradoxes are an argument against its possibility, they are not a knock-out blow. After all, paradoxes arise quite naturally in the real world. Take Bertrand Russell's grouping paradox, which blew his mind so much that he abandoned his current research and divorced his wife. Or the simple sentence "This sentence is false." You don't need a time machine to create it, just a pen and paper. Or a voice, for that matter.
To me, the most damning evidence against the possibility of time travel is a combination of two facts. First, the fact that time moves inexorably forwards, and always has. Second, there's no hard evidence that anything else is possible. Hume's dictum "extraordinary claims require extraordinary evidence," tends to rule it out. Indeed there are theoretical reasons for believing in it, but no evidentiary ones.
And purely theoretical claims seem to me to be prone to unseen fallibilities.
Zeno's paradox looks particularly good on paper, for example. According to Aristotle, Zeno's paradox goes like this:

In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.

The classic scenario is a race between Achilles and a tortoise. The tortoise gets a hundred foot headstart. Achilles runs as fast as he can. When he gets to where the tortoise started, the tortoise has traveled ten feet. Achilles keeps running, but when he gets ten feet further, the tortoise has gone another foot. Achilles keeps running, but the tortoise has moved on again. It seems he can never catch the tortoise.
Of course, Zeno's paradox is not a paradox at all: it is simply a clever illusion created by the way the race is described. Mathematicians have had a lot of fun with finding explanations for it. I mention Zeno's paradox not to draw parallels with time travel paradoxes or the like. Rather, it is an example of a situation where the way you look at something can lead you astray.
Perhaps the way Einstein described time - it’s just another dimension - encourages us to look at time the wrong way, like a room we don’t have the key to. And perhaps thinking of time as "on a line" - like a historical timeline - encourages us to imagine something you can walk back and forth along, when in fact, an arrow or a wave might be more appropriate.
Some metaphors make time travel seem quite possible. Other metaphors, like the arrow, make the idea not just impossible, but incomprehensible. Are our metaphors locking us in or out (to use another metaphor)? Metaphors drive intuitions, especially scientific intuitions.
Perhaps it’s an arrow, perhaps it’s a river, perhaps it’s an hourglass. Perhaps it’s a road with traffic in both directions.
My money is on the arrow.

"We all have our time machines. Some take us back, they're called memories. Some take us forward, they're called dreams." -Jeremy Irons in The Time Machine (2002)