of space, he suggests, it must be part of any possible reality—a necessary existent, like God, or Henri Bergson’s inner self.
So is space to be our great bulwark against nothingness? Rundle hedges his bets. At one point he considers an alternative argument, to the effect that the very idea of nothingness is incoherent. If there were nothing, then it would have been a fact that there was nothing. So at least one thing would exist after all: that fact! (This is a truly terrible argument; the enumeration of its fallacies is left as an exercise for the reader.) But it is space that Rundle keeps coming back to, since he just can’t think it away, try as he might. “Space is not nothing,” he insists, “it is something you can stare into or travel through, something of which there can be volumes.”
Not everyone shares Rundle’s conviction that space is a something. Among philosophers, there are two competing views of what space actually is. (To be scientifically up-to-date, we should be talking about “spacetime” rather than “space,” but no matter.) One of them, the substantival view, goes back to Newton. It holds that space is indeed a real thing, with its own intrinsic geometry, and that it would continue to exist even if all its contents vanished. The other view of space, the relational view, goes back to Newton’s great rival, Leibniz. It holds that space is not a thing unto itself, but merely a web of relations among things. Space could no more exist apart from the things that it relates, on Leibniz’s view, than the grin of the Cheshire Cat could exist apart from the feline itself.
The ontological debate between the Newtonians and the Leibnizians continues to the present day, and it’s a lively one. Relativity theory, in which spacetime affects the behavior of matter, has tipped the balance somewhat in favor of the substantivalists.
But it’s not necessary to resolve this debate to see whether the container argument is any good. Suppose the relationists are right, and space is just a convenient theoretical fiction. In that case, if the contents of the cosmos were to vanish, space would vanish along with them, leaving absolute nothingness.
Now suppose, contrariwise, that the substantivalists are right. Suppose that space is a genuine cosmic arena, with an existence all its own. Then this arena could survive the disappearance of its material contents. Even with everything gone, there would still be unoccupied positions. But if space has real objective existence, so does its geometrical form. It could be infinite in extent. But it could also be finite, even though it has no boundary. (The surface of a basketball, for example, is a finite two-dimensional space that has no boundary.) Such “closed” spacetimes are consistent with Einstein’s relativity theory. Indeed, Stephen Hawking and other cosmologists have theorized that the spacetime of our own universe is finite and unbounded, like a higher-dimensional analogue to the surface of a basketball. In that case, it is not hard to “think away” spacetime along with everything in it. Just imagine that basketball deflating, or rather shrinking. In your mind’s eye, the finite radius of the basketball-cosmos grows smaller and smaller until, finally, it reaches zero. Now the spacetime arena itself has vanished, leaving absolute nothingness behind.
This thought experiment leads to an elegant scientific definition (originally due to the physicist Alex Vilenkin):
Nothingness = a closed spherical spacetime of zero radius
So the container argument fails, regardless of what the nature of the container might turn out to be. If spacetime is not a genuine entity, but merely a set of relations among things, then it vanishes along with those things and hence is no obstacle to the possibility of nothingness. If spacetime is a genuine entity, with its own peculiar structure and quiddity, then it can be “disappeared” by the imagination just like the rest of the furniture of reality.
Voiding reality in the mind’s eye is a purely imaginative achievement. What if one tried to carry it out in the lab? Aristotle thought that this would be impossible. He produced a variety of arguments, both empirical and conceptual, purporting to show that you can’t empty out a region of space. The Aristotelian orthodoxy that “nature abhors a vacuum” held until the middle of the seventeenth century, when it was decisively overthrown by one of Galileo’s pupils, Evangelista Torricelli. An ingenious experimentalist, Torricelli had the happy idea of pouring mercury into a test tube, and then, with his finger over the open end,