There is no singularly real world of thought; each mind evolves its own internal universe. The worlds of thought that we appear to like the best are those where goals and actions seem to mesh in regions large enough to spend our lives in — and thus become a Buddhist, or Republican, or poet, or topologist. Some mental starting points grow into great, coherent continents. In certain parts of mathematics, science, and philosophy, a relatively few but clear ideas may lead into an endless realm of complex yet consistent new structures. Yet even in mathematics, a handful of seemingly innocent rules can lead to complications far beyond our grasp. Thus we feel we understand perfectly the rules of addition and multiplication — yet when we mix them together, we encounter problems about prime numbers that have remained unsolved for centuries.
Minds also make up pleasant worlds of practical affairs — which work because we make them work, by putting things in order there. In the physical realm, we keep our books and clothes in self-made shelves and cabinets — thus building artificial boundaries to keep our things from interacting very much. Similarly, in mental realms, we make up countless artificial schemes to force things to seem orderly, by specifying legal codes, grammar rules and traffic laws. When growing up in such a world, it all seems right and natural — and only scholars and historians recall the mass of precedents and failed experiments it took to make it work so well. These natural worlds are actually more complex than the technical worlds of philosophy. They're far too vast to comprehend — except where we impose on them the rules we make.
There is also a different and more sinister way to make the world seem orderly, in which the mind has merely found a way to simplify itself. This is what we must suspect whenever some idea seems to explain too much. Perhaps no problem was actually solved at all; instead, the mind has merely found some secondary pathway in the brain, through which one can mechanically dislodge each doubt and difference from its rightful place! This may be what happens in some of those experiences that leave a person with a sense of revelation — in a state in which no doubts remain, or with a vision of astounding clarity — yet unable to recount any details. Some accident of mental stress has temporarily suppressed the capacity to question, doubt, or probe. One remembers that no questions went unanswered but forgets that none were asked! One can acquire certainty only by amputating inquiry.
When victims of these incidents become compelled to recapture them, their lives and personalities are sometimes permanently changed. Then others, seeing the radiance in their eyes and hearing of the glory to be found, are drawn to follow them. But to offer hospitality to paradox is like leaning toward a precipice. You can find out what it is like by falling in, but you may not be able to fall out again. Once contradiction finds a home, few minds can spurn the sense-destroying force of slogans such as all is one.