There is no possible way that our stock of knowledge can ever be adequate. The world never stops changing. Novel situations continue to emerge. We will always be learning something new.
If we make enough areas of life routine, however, the activity in the warehouse of ideas can come to a near standstill. This can happen if we lead a dull, simple life with a minimum of novelty, or if we choose the "fast" lifestyle of compulsive, readymade, culturally sanctioned (though not necessarily condoned) activities. Both are a defense against anxiety.
The dull life is essentially an escape to what was the only life before the scientific, technicized world made possible the anxiety-engendering environment we live in today. The fast life — only possible in a technological world — turns the problem into a solution by incorporating anxiety, endless novelty, and the romance of danger into a lifestyle.
If we live the fast life we can get by with a stagnant stock of knowledge partly because we assume life is short. If we choose the dull quiet life, on the other hand, the major decisions — career, marriage, family, where to live — have been solved once and for all. We assume we won’t have to think much about them again, that they’re no longer open to question.
But for most people, who live neither in cloistered nostalgia nor in the fast lane, the stock of knowledge is continuously updated. We are always learning, always phasing out dated items. There is always more we could know. This is our negative knowledge.
Although we’re always ignorant of the content of what we don’t yet know, sometimes we can see the empty shell of negative knowledge before it has been filled in with specific details. If I go to look up your phone number, I know it will have seven digits, but not which ones. If you are reading a book and are interrupted, the unread portion of the book is an empty category you’ll return to and fill in later. Categories are always relatively empty compared to the real thing. The idea "dog" is devoid of specific content, but a live golden retriever wagging her tail and drooling on my bare foot leaves little to imagination.
We know there are things we don’t know — information we’ll learn in the future, events that are insignificant and irrelevant, secrets that go to the grave. But there are two kinds of negative knowledge: what we know we don’t know (empty categories), and what we don’t know we don’t know (true ignorance).
We tend to lump all negative knowledge together, regarding everything we don’t know as inaccessible for technical reasons. After all, we can’t expect our present knowledge to be adequate for all situations. We’ve only had so much time in which to acquire experience and knowledge. We can’t be in two places at once. In the course of a lifetime we may have seen Paris, Munich, and Tokyo — but not Moscow. We may have learned how to ride a horse, milk a cow, and shear sheep; but we may not have learned automobile repair, hairdressing, and bookkeeping. If we spend time in contemplative, intellectual, creative pursuits, we may have sacrificed a social life.
The actual course of a life is a succession of situations that stand out against a background of possible experiences: the alternatives we reject, the accidents we avoid, the opportunities we miss. There’s a practical limit to what we could know. We assume that what happens to be unknown is in principle knowable — or would be known if we had lived our lives differently.
We regard even the future as unknown only for a technical reason: we have to wait for it to arrive. Even when I become aware of my past ignorance — perhaps I used to believe that rabbits laid eggs — I regard this as an isolated incident in an otherwise sufficient understanding of the world. It’s possible to regard every individual case as an example of a temporary deficiency. Taken one by one, we can always find an explanation for our ignorance once we become aware of it.
What we don’t admit is that we’re not dealing with special cases at all. What we consider a technical inadequacy in one situation is in fact a characteristic of all knowledge. All "definitive" solutions are subject to change. Whatever we know today borders on how we will know it differently in the future. Creationism, horse-drawn carriages, candles, silent films, and black and white television were as taken for granted in their time as their descendants are today.
In practice there’s no reason to suspect that any particular piece of information is inadequate before it is revealed to be otherwise. But in theory there’s no reason to exclude anything from suspicion. Everything is equally suspect. It is characteristic of all interpretations, meanings, and values that they are never the last word. They are all potentially obsolete. Reality is not just occasionally precarious — it has no permanent foundations whatsoever. It is the nature of knowledge to be fragmentary and partial. This is the first and final, the ultimate source of anxiety.
All the experience that goes into building up a stock of knowledge is acquired in real situations. As we’ve already seen, we stop interpreting and considering a situation as soon as our practical interest is satisfied. The contours that define the boundaries of our knowledge and give it a particular shape are determined by the negative knowledge just out of reach. In the problems of everyday life we sense this negative knowledge. We’re anxious when we suspect change is coming and don’t yet know what it will be. As some people feel the change in weather in their joints, we feel the loosening of our grip on reality in the barometer of discomfort that measures our anxiety.
The fringe of negative knowledge that surrounds what we know blends into the region of the fundamentally opaque and unknowable, what is beyond our ability to grasp. Every relative insufficiency of knowledge refers to the more basic inadequacy of a humanly created world. Negative knowledge imperceptibly shades into the inexpressible limits of knowledge. Everyday anxiety is the first drop of what could turn into a flood of realization that would drain the reservoir of meaning — the recognition that all meaning and value is arbitrary.