Philosophers love to talk about Nothing.

And when they do, it is often unclear what, if anything, they are talking about.

The concept of Nothing is not the same as the concept of negation. These letters are not a dog, nor the moon, nor are they purple, but Nothing is not anything. It is often noted that thinking of a thing involves, in some way, what it is not, its negation. Does thinking of anything involve, in some way, thinking of Nothing?

Many contemporary philosophers think that the whole idea that Nothing is a thing that can be pondered is itself a grammatical mistake. Just because I can use the word “Nothing” as a grammatical subject in a sentence in the same way I use other nouns, doesn’t mean that the word designates a thing. The words “all” and “nothing” are typically not thought to be nouns, but logical operators that say something about things that have certain properties. “All dogs are mammals” means that if a thing is a dog, then it is a mammal too. “Nothing is a round square” means that if a thing is round it is not also square. So Nothing, on this view, is only a way of denying certain properties to the things that exist. It is not a thing in itself, nor, certainly, is it a way of talking about the absence of all things. When we try to talk about Nothing itself, there is really nothing to talk about.

But this seems too easy a way to dispose of the problem. Even if you get rid of everything, Nothing is there. You never really know what you have until it’s gone. Surely if appreciating the contingency of a thing involves seeing it against the background of its negation or absence, then appreciating the contingency of everything, the world as a whole, means seeing it against the background of Nothing. Even if the logical operators “all” and “nothing” are limited to talking about things with certain properties, we can conceive of things that might transcend all our properties. Plotinus thought that the One was beyond Being; Christians believe that God created the universe from Nothing. Appreciating the contingency of this world means asking why there is something rather than Nothing. But if the answer to that question involves something that transcends all of our properties, is it really nothing? Though thinking about Nothing leads to thoughts of the source of all things, it seems that Nothing is the absence of anything, even of things we can’t talk about.

Thinking about this kind of Nothing presents special problems. If we stop thinking of anything, have we stopped thinking, or are we thinking of Nothing. Try to think of Nothing. When you do, you find that you are thrown back into the thought of particular things. But are those things the same, or have they been transformed by the attempt to think away their existence, by the encounter with Nothingness? The classic account of the role of Nothing in consciousness was given by Martin Heidegger in “What is Metaphysics.” He held that when we lose all our focus on things around us, Nothing looms just over the horizon of our consciousness. When we try to approach it we are thrown back into our thought of things. “The nothing itself does not attract; it is essentially repelling. . . . This wholly repelling gesture toward beings that are in retreat as a whole, which is the action of the nothing that oppresses Dasein in anxiety, is the essence of the nothing: nihilation. … The nothing itself nihilates.” The brush with the nothingness behind all things pushes us back to life with a renewed sense of the radical contingency of their existence rather than Nothing. Heidegger says “Nihilation is not some fortuitous incident. Rather, as the repelling gesture toward the retreating whole of beings, it discloses these beings in their full but heretofore concealed strangeness as what is radically other — with respect to the nothing. In the clear night of the nothing of anxiety the original openness of beings as such arises: that they are beings — and not nothing. . . .” Nothing, it seems, is the key to everything.

The next time someone asks you what you are thinking, “Nothing” should not seem like such an empty answer.

But, as my favorite “Nothing” joke goes, “Nobody understands Nothing. . . . But , then again, he would!”

(Tuesday, September 26, is the 117th anniversary of the birth of Martin Heidegger in 1889. I’m sure nothing would have pleased him more than to have us remember him in this way.)