Why Does the World Exist: An Existentia - By Jim Holt Page 0,23

plunging it into a mercury bath. With the tube standing vertically upside down, a little airless void appeared above the column of mercury. What Torricelli had done was to create the first barometer. He had also demonstrated that nature’s supposed horror vacui was really nothing more than the weight of the atmospheric air pressing down on us.

But did Torricelli succeed in producing a bit of true nothingness? Not quite. Today, we know that the sort of airless space he was the first to create is far from being completely empty. The most perfect vacuum, it turns out, still contains something. In physics, the notion of “something” is quantified by energy. (Even matter, as Einstein’s most famous equation shows, is just frozen energy.) Physically speaking, space is as empty as it can be when it is devoid of energy.

Now, suppose you try to remove every bit of energy from a region of space. Suppose, in other words, you try to reduce that region to its state of lowest energy, which is known as its “vacuum state.” At a certain point in this energy-draining process, something very counterintuitive will occur. An entity that physicists call the “Higgs field” will spontaneously emerge. And this Higgs field cannot be got rid of, because its contribution to the total energy of the space you are trying to empty out is actually negative. The Higgs field is a “something” that contains less energy than a “nothing.” And it is accompanied by a riot of “virtual particles” that ceaselessly wink in and out of existence. Space in a vacuum state turns out to be very busy indeed, rather like Times Square on New Year’s Eve.

PHILOSOPHERS WHO BELIEVE in Nothing—they sometimes call themselves “metaphysical nihilists”—try to steer clear of such physical snags. In the late 1990s, several British and American philosophers jointly pioneered what has become known as the “subtraction argument.” Unlike the observer and container arguments, which were anti-nothingness, the subtraction argument is pro-nothingness. It is meant to demonstrate that an absolute void is a genuine metaphysical possibility.

The subtraction argument begins by assuming, plausibly enough, that the world contains a finite number of objects—people, tables, chairs, rocks, and so forth. It also assumes that each of these objects is contingent: although the object does in fact exist, it might not have existed. This too seems plausible. Think of the movie It’s a Wonderful Life, and its protagonist George Bailey (played by Jimmy Stewart). After a series of setbacks in his life, George finds himself contemplating suicide. Thanks to the intervention of an angel named Clarence, George gets to see what the world would have looked like if he had never been born. He is confronted with the contingency of his own existence. The same contingency seems to infect not only individual people, but also the entire inventory of actually existing things, from the Milky Way to the Eiffel Tower to the dog sleeping on your sofa to the speck of dust on the mousepad of your laptop. Each of these things, although it happens to exist, might not have existed if the cosmos had unfolded differently. Finally, the subtraction argument makes an assumption of independence: that the nonexistence of one thing does not necessitate the existence of anything else.

With all three of these premises in place—finiteness, contingency, and independence—it is easy to derive the conclusion that there might have been nothing at all. You simply subtract each contingent object from the world, one by one, until you end up with absolute emptiness, a pure void. This “subtraction” is supposed to be metaphorical rather than literal. Each stage of the argument asserts a relationship between possible worlds: if a world with n objects is possible, then a world with n−1 objects is also possible. At the penultimate stage in the subtraction process, the world might consist of no more than a single grain of sand. If such a sad little world is possible, then so is a world where that grain of sand is deleted—a world of nothingness.

The subtraction argument is generally considered to be the strongest one in the arsenal of the metaphysical nihilists. Indeed, it may be the only positive argument they have. Although I have stated the argument somewhat crudely, its proponents have painstakingly put it into a form where it appears to be logically valid: no mean feat. If the premises are true, the conclusion—that absolute nothingness is possible—must also be true.

But are the premises of the subtraction argument true? In other words, is