All the un fun kinds of wealth creation slow dramatically in a society that confiscates private fortunes. We can confirm this empirically. Suppose you hear a strange noise that you think may be due to a nearby fan. You turn the fan off, and the noise stops. You turn the fan back on, and the noise starts again. Off, quiet. On, noise. In the absence of other information, it would seem the noise is caused by the fan.

At various times and places in history, whether you could acc.u.mulate a fortune by creating wealth has been turned on and off. Northern Italy in 800, off (warlords would steal it). Northern Italy in 1100, on. Central France in 1100, off (still feudal). England in 1800, on. England in 1974, off (98% tax on investment income). United States in 1974, on. We"ve even had a twin study: West Germany, on; East Germany, off. In every case, the creation of wealth seems to appear and disappear like the noise of a fan as you switch on and off the prospect of keeping it.

There is some momentum involved. It probably takes at least a generation to turn people into East Germans (luckily for England). But if it were merely a fan we were studying, without all the extra baggage that comes from the controversial topic of wealth, no one would have any doubt that the fan was causing the noise.

If you suppress variations in income, whether by stealing private fortunes, as feudal rulers used to do, or by taxing them away, as some modern governments have done, the result always seems to be the same. Society as a whole ends up poorer.

If I had a choice of living in a society where I was materially much better off than I am now, but was among the poorest, or in one where I was the richest, but much worse off than I am now, I"d take the first option. If I had children, it would arguably be immoral not to. It"s absolute poverty you want to avoid, not relative poverty. If, as the evidence so far implies, you have to have one or the other in your society, take relative poverty.

You need rich people in your society not so much because in spending their money they create jobs, but because of what they have to do to get rich. I"m not talking about the trickle-down effect here. I"m not saying that if you let Henry Ford get rich, he"ll hire you as a waiter at his next party. I"m saying that he"ll make you a tractor to replace your horse.

Chapter 8. A Plan for Spam.

I think it"s possible to stop spam, and that content-based filters are the way to do it. The Achilles heel of the spammers is their message. They can circ.u.mvent any other barrier you set up. They have so far, at least. But they have to deliver their message, whatever it is. If we can write software that recognizes their messages, there is no way they can get around that.

To the recipient, spam is easily recognizable. If you hired someone to read your mail and discard the spam, they would have little trouble doing it. How much do we have to do, short of AI, to automate this process?

I think we will be able to solve the problem with fairly simple algorithms. In fact, I"ve found that you can filter present-day spam acceptably well using nothing more than a Bayesian combination of the spam probabilities of individual words. Using a slightly tweaked (as described below) Bayesian filter, we now miss less than 5 per 1000 spams, with 0 false positives.

The statistical approach is not usually the first one people try when they write spam filters. Most hackers" first instinct is to try to write software that recognizes individual properties of spam. You look at spams and you think, the gall of these guys to try sending me mail that begins "Dear Friend" or has a subject line that"s all uppercase and ends in eight exclamation points. I can filter out that stuff with about one line of code.

And so you do, and in the beginning it works. A few simple rules will take a big bite out of your incoming spam. Merely looking for the word click will catch 79.7% of the emails in my spam corpus, with only 1.2% false positives.

I spent about six months writing software that looked for individual spam features before I tried the statistical approach. What I found was that recognizing that last few percent of spams got very hard, and that as I made the filters stricter I got more false positives.

False positives are innocent emails that get mistakenly identified as spams. For most users, missing legitimate email is an order of magnitude worse than receiving spam, so a filter that yields false positives is like an acne cure that carries a risk of death to the patient.

The more spam a user gets, the less likely he"ll be to notice one innocent mail sitting in his spam folder. And strangely enough, the better your spam filters get, the more dangerous false positives become, because when the filters are really good, users will be more likely to ignore everything they catch.

I don"t know why I avoided trying the statistical approach for so long. I think it was because I got addicted to trying to identify spam features myself, as if I were playing some kind of compet.i.tive game with the spammers. (Nonhackers don"t often realize this, but most hackers are very compet.i.tive.) When I did try statistical a.n.a.lysis, I found immediately that it was much cleverer than I had been. It discovered, of course, that terms like virtumundo and teens were good indicators of spam. But it also discovered that per and FL and ff0000 are good indicators of spam. In fact, ff0000 (HTML for bright red) turns out to be as good an indicator of spam as any p.o.r.nographic term.

Here"s a sketch of how I do statistical filtering. I start with one corpus of spam and one of non spam mail. At the moment each one has about 4000 messages in it. I scan the entire text, including headers and embedded HTML and Javascript, of each message in each corpus. I currently consider alphanumeric characters, dashes, apostrophes, and dollar signs to be part of tokens, and everything else to be a token separator. (There is probably room for improvement here.) I ignore tokens that are all digits, and I also ignore HTML comments, not even considering them as token separators.

I count the number of times each token (ignoring case, currently) occurs in each corpus. At this stage I end up with two large hash tables, one for each corpus, mapping tokens to number of occurrences.

Next I create a third hash table, this time mapping each token to the probability that an email containing it is a spam, Pspam|w which I calculate as follows: r g = min (1, 2(good (w)/G)), rb = min (1, bad (w)/B) Pspam|w = max(.01,min (.99, rb /( rg + rb ))) where w is the token whose probability we"re calculating, good and bad are the hash tables I created in the first step, and G and B are the number of non spam and spam messages respectively.

I want to bias the probabilities slightly to avoid false positives, and by trial and error I"ve found that a good way to do it is to double all the numbers in good. This helps to distinguish between words that occasionally do occur in legitimate email and words that almost never do. I only consider words that occur more than five times in total (actually, because of the doubling, occurring three times in non spam mail would be enough). And then there is the question of what probability to a.s.sign to words that occur in one corpus but not the other. Again by trial and error I chose .01 and .99. There may be room for tuning here, but as the corpus grows such tuning will happen automatically anyway.

The especially observant will notice that while I consider each corpus to be a single long stream of text for purposes of counting occurrences, I use the number of emails in each, rather than their combined length, as the divisor in calculating spam probabilities. This adds another slight bias to protect against false positives.

When new mail arrives, it is scanned into tokens, and the most interesting fifteen tokens, where interesting is measured by how far their spam probability is from a neutral .5, are used to calculate the probability that the mail is spam. If w1, . . . , w15 are the fifteen most interesting tokens, you calculate the combined probability thus: Figure 8-1.

One question that arises in practice is what probability to a.s.sign to a word you"ve never seen, i.e. one that doesn"t occur in the hash table of word probabilities. I"ve found, again by trial and error, that .4 is a good number to use. If you"ve never seen a word before, it is probably fairly innocent; spam words tend to be all too familiar.

I treat mail as spam if the algorithm above gives it a probability of more than .9 of being spam. But in practice it would not matter much where I put this threshold, because few probabilities end up in the middle of the range.

One great advantage of the statistical approach is that you don"t have to read so many spams. Over the past six months, I"ve read literally thousands of spams, and it is really kind of demoralizing. Norbert Wiener said if you compete with slaves you become a slave, and there is something similarly degrading about competing with spammers. To recognize individual spam features you have to try to get into the mind of the spammer, and frankly I want to spend as little time inside the minds of spammers as possible.

But the real advantage of the Bayesian approach, of course, is that you know what you"re measuring. Feature-recognizing filters like Spam a.s.sa.s.sin a.s.sign a spam "score" to email. The Bayesian approach a.s.signs an actual probability. The problem with a "score" is that no one knows what it means. The user doesn"t know what it means, but worse still, neither does the developer of the filter. How many points should an email get for having the word s.e.x in it? A probability can of course be mistaken, but there is little ambiguity about what it means, or how evidence should be combined to calculate it. Based on my corpus, s.e.x indicates a .97 probability of the containing email being a spam, whereas s.e.xy indicates .99 probability. And Bayes"s Rule, equally unambiguous, says that an email containing both words would, in the (unlikely) absence of any other evidence, have a 99.97% chance of being a spam.

Because it is measuring probabilities, the Bayesian approach considers all the evidence in the email, both good and bad. Words that occur disproportionately rarely in spam (like though or tonight or apparently) contribute as much to decreasing the probability as bad words like unsubscribe and opt-in do to increasing it. So an otherwise innocent email that happens to include the word s.e.x is not going to get tagged as spam.

Ideally, of course, the probabilities should be calculated individually for each user. I get a lot of email containing the word Lisp, and (so far) no spam that does. So a word like that is effectively a kind of pa.s.sword for sending mail to me. In my earlier spam-filtering software, the user could set up a list of such words and mail containing them would automatically get past the filters. On my list I put words like Lisp and also my zipcode, so that (otherwise rather spammy-sounding) receipts from online orders would get through. I thought I was being very clever, but I found that the Bayesian filter did the same thing for me, and moreover discovered of a lot of words I hadn"t thought of.

When I said at the start that our filters let through less than 5 spams per 1000 with 0 false positives, I"m talking about filtering my mail based on a corpus of my mail. But these numbers are not misleading, because that is the approach I"m advocating: filter each user"s mail based on the spam and non spam mail he receives. Essentially, each user should have two delete b.u.t.tons, ordinary delete and delete-as-spam. Anything deleted as spam goes into the spam corpus, and everything else goes into the non spam corpus.

You could start users with a seed filter, but ultimately each user should have his own per-word probabilities based on the actual mail he receives. This (a) makes the filters more effective, (b) lets each user decide their own precise definition of spam, and (c) perhaps best of all makes it hard for spammers to tune mails to get through the filters. If a lot of the brain of the filter is in the individual databases, then merely tuning spams to get through the seed filters won"t guarantee anything about how well they"ll get through individual users" varying and much more trained filters.

Content-based spam filtering is often combined with a white list, a list of senders whose mail can be accepted with no filtering. One easy way to build such a white list is to keep a list of every address the user has ever sent mail to. If a mail reader has a delete as spam b.u.t.ton then you could also add the from address of every email the user has deleted as ordinary trash.

I"m an advocate of white lists, but more as a way to save computation than as a way to improve filtering. I used to think that white lists would make filtering easier, because you"d only have to filter email from people you"d never heard from, and someone sending you mail for the first time is constrained by convention in what they can say to you. Someone you already know might send you an email talking about s.e.x, but someone sending you mail for the first time would not be likely to. The problem is, people can have more than one email address, so a new from address doesn"t guarantee that the sender is writing to you for the first time. It is not unusual for an old friend (especially if he is a hacker) to suddenly send you an email with a new from-address, so you can"t risk false positives by filtering mail from unknown addresses especially stringently.

In a sense, though, my filters do themselves embody a kind of white list (and blacklist) because they are based on entire messages, including the headers. So to that extent they "know" the email addresses of trusted senders and even the routes by which mail gets from them to me. And they know the same about spam, including the server names, mailer versions, and protocols.

If I thought that I could keep up current rates of spam filtering, I would consider this problem solved. But it doesn"t mean much to be able to filter out most present-day spam, because spam evolves. Indeed, most anti spam techniques so far have been like pesticides that do nothing more than create a new, resistant strain of bugs.

I"m more hopeful about Bayesian filters, because they evolve with the spam. So as spammers start using v1agra instead of v.i.a.g.r.a to evade simple-minded spam filters based on individual words, Bayesian filters automatically notice. Indeed, v1agra is far more d.a.m.ning evidence than v.i.a.g.r.a, and Bayesian filters know precisely how much more.

Still, anyone who proposes a plan for spam filtering has to be able to answer the question: if the spammers knew exactly what you were doing, how well could they get past you? For example, I think that if checksum-based spam filtering becomes a serious obstacle, the spammers will just switch to mad-lib techniques for generating message bodies.

To beat Bayesian filters, it would not be enough for spammers to make their emails unique or to stop using individual naughty words. They"d have to make their mails indistinguishable from your ordinary mail. And this I think would severely constrain them. Spam is mostly sales pitches, so unless your regular mail is all sales pitches, spams will inevitably have a different character. And the spammers would also, of course, have to change (and keep changing) their whole infrastructure, because otherwise the headers would look as bad to the Bayesian filters as ever, no matter what they did to the message body. I don"t know enough about the infrastructure that spammers use to know how hard it would be to make the headers look innocent, but my guess is that it would be even harder than making the message look innocent.

a.s.suming they could solve the problem of the headers, the spam of the future will probably look something like this: Hey there. Check out the following: www.27meg.com/foo because that is about as much sales pitch as content-based filtering will leave the spammer room to make. (Indeed, it will be hard even to get this past filters, because if everything else in the email is neutral, the spam probability will hinge on the URL, and it will take some effort to make that look neutral.) Spammers range from businesses running so-called opt-in lists who don"t even try to conceal their ident.i.ties, to guys who hijack mail servers to send out spams promoting p.o.r.n sites. If we use filtering to whittle their options down to mails like the one above, that should pretty much put the spammers on the "legitimate" end of the spectrum out of business; they feel obliged by various state laws to include boilerplate about why their spam is not spam, and how to cancel your "subscription," and that kind of text is easy to recognize.

(I used to think it was naive to believe that stricter laws would decrease spam. Now I think that while stricter laws may not decrease the amount of spam that spammers send, they can certainly help filters to decrease the amount of spam that recipients actually see.) All along the spectrum, if you restrict the sales pitches spammers can make, you will inevitably tend to put them out of business. That word business is an important one to remember. The spammers are businessmen. They send spam because it works. It works because although the response rate is abominably low (at best 15 per million, vs. 3000 per million for a catalog mailing), the cost, to them, is practically nothing. The cost is enormous for the recipients, about 5 man-weeks for each million recipients who spend a second to delete the spam, but the spammer doesn"t have to pay that.

Sending spam does cost the spammer something, though. So the lower we can get the response rate-whether by filtering, or by using filters to force spammers to dilute their pitches-the fewer businesses will find it worth their while to send spam.

The reason the spammers use the kinds of sales pitches that they do is to increase response rates. This is possibly even more disgusting than getting inside the mind of a spammer, but let"s take a quick look inside the mind of someone who responds to a spam. This person is either astonishingly credulous or deeply in denial about their s.e.xual interests. In either case, repulsive or idiotic as the spam seems to us, it is exciting to them. The spammers wouldn"t say these things if they didn"t sound exciting. And "check out the following" is just not going to have nearly the pull with the spam recipient as the kinds of things that spammers say now. Result: if it can"t contain exciting sales pitches, spam becomes less effective as a marketing vehicle, and fewer businesses want to use it.

That is the big win in the end. I started writing spam filtering software because I didn"t want have to look at the stuff anymore. But if we get good enough at filtering out spam, it will stop working, and the spammers will actually stop sending it.

Of all the approaches to fighting spam, from software to laws, I believe Bayesian filtering will be the single most effective. But I also think that the more different kinds of anti spam efforts we undertake, the better, because any measure that constrains spammers will tend to make filtering easier. And even within the world of content-based filtering, I think it will be a good thing if there are many different kinds of software being used simultaneously. The more different filters there are, the harder it will be for spammers to tune spams to get through them.

Chapter 9. Taste for Makers.

Copernicus" aesthetic objections to [equants] provided one essential motive for his rejection of the Ptolemaic system. ...

THOMAS KUHN, The Copernican Revolution All of us had been trained by Kelly Johnson and believed fanatically in his insistence that an airplane that looked beautiful would fly the same way.

BEN RICH, Skunk Works Beauty is the first test: there is no permanent place in this world for ugly mathematics.

G. H. HARDY, A Mathematician"s Apology I was talking recently to a friend who teaches at MIT. His field is hot now and every year he is inundated by applications from would-be graduate students. "A lot of them seem smart," he said. "What I can"t tell is whether they have any kind of taste."

Taste. You don"t hear that word much now. And yet we still need the underlying concept, whatever we call it. What my friend meant was that he wanted students who were not just good technicians, but who could use their technical knowledge to design beautiful things.

Mathematicians call good work "beautiful," and so, either now or in the past, have scientists, engineers, musicians, architects, designers, writers, and painters. Is it just a coincidence that they used the same word, or is there some overlap in what they meant? If there is an overlap, can we use one field"s discoveries about beauty to help us in another?

For those of us who design things, these are not just theoretical questions. If there is such a thing as beauty, we need to be able to recognize it. We need good taste to make good things. Instead of treating beauty as an airy abstraction, to be either blathered about or avoided depending on how one feels about airy abstractions, let"s try considering it as a practical question: how do you make good stuff?

If you mention taste nowadays, a lot of people will tell you that "taste is subjective." They believe this because it really feels that way to them. When they like something, they have no idea why. It could be because it"s beautiful, or because their mother had one, or because they saw a movie star with one in a magazine, or because they know it"s expensive. Their thoughts are a tangle of unexamined impulses.

Most of us were encouraged, as children, to leave this tangle unexamined. If you made fun of your little brother for coloring people green in his coloring book, your mother was likely to tell you something like "you like to do it your way and he likes to do it his way."

Your mother at this point was not trying to teach you important truths about aesthetics. She was trying to get the two of you to stop bickering.

Like many of the half-truths adults tolds us, this one contradicts other things they told us. After dinning into you that taste is merely a matter of personal preference, they took you to the museum and told you that you should pay attention because Leonardo is a great artist.

What goes through the kid"s head at this point? What does he think "great artist" means? After having been told for years that everyone just likes to do things their own way, he is unlikely to head straight for the conclusion that a great artist is someone whose work is better than the others". A far more likely theory, in his Ptolemaic model of the universe, is that a great artist is something that"s good for you, like broccoli, because someone said so in a book.

Saying that taste is just personal preference is a good way to prevent disputes. The trouble is, it"s not true. You feel this when you start to design things.

Whatever job people do, they naturally want to do better. Football players like to win games. CEOs like to increase earnings. It"s a matter of pride, and a real pleasure, to get better at your job. But if your job is to design things, and there is no such thing as beauty, then there is no way to get better at your job. If taste is just personal preference, then everyone"s is already perfect: you like whatever you like, and that"s it.

As in any job, as you continue to design things, you"ll get better at it. Your tastes will change. And, like anyone who gets better at their job, you"ll know you"re getting better. If so, your old tastes were not merely different, but worse. Poof goes the axiom that taste can"t be wrong.

Relativism is fashionable at the moment, and that may hamper you from thinking about taste, even as yours grows. But if you come out of the closet and admit, at least to yourself, that there is such a thing as good design, then you can start to study it in detail. How has your taste changed? When you made mistakes, what caused you to make them? What have other people learned about design?

Once you start to examine the question, it"s surprising how much different fields" ideas of beauty have in common. The same principles of good design crop up again and again.

GOOD DESIGN IS SIMPLE. You hear this from math to painting. In math it means that a shorter proof tends to be a better one. Where axioms are concerned, especially, less is more. It means much the same thing in programming. For architects and designers, it means that beauty should depend on a few carefully chosen structural elements rather than a profusion of superficial ornament. (Ornament is not in itself bad, only when it"s camouflage on insipid form.) Similarly, in painting, a still life of a few carefully observed and solidly modelled objects will tend to be more interesting than a stretch of flashy but mindlessly repet.i.tive painting of, say, a lace collar. In writing it means: say what you mean and say it briefly.

It seems strange to have to emphasize simplicity. You"d think simple would be the default. Ornate is more work. But something seems to come over people when they try to be creative. Beginning writers adopt a pompous tone that doesn"t sound anything like the way they speak. Designers trying to be artistic resort to swooshes and curlicues. Painters discover that they"re expressionists. It"s all evasion. Underneath the long words or the "expressive" brush strokes, there"s not much going on, and that"s frightening.

When you"re forced to be simple, you"re forced to face the real problem. When you can"t deliver ornament, you have to deliver substance.

GOOD DESIGN IS TIMELESS. In math, every proof is timeless unless it contains a mistake. So what does Hardy mean when he says there is no permanent place for ugly mathematics? He means the same thing Kelly Johnson did: if something is ugly, it can"t be the best solution. There must be a better one, and eventually someone else will discover it.

Aiming at timelessness is a way to make yourself find the best answer: if you can imagine someone surpa.s.sing you, you should do it yourself. Some of the greatest masters did this so well that they left little room for those who came after. Every engraver since Durer suffers by comparison.

Aiming at timelessness is also a way to evade the grip of fashion. Fashions almost by definition change with time, so if you can make something that will still look good far into the future, then its appeal must derive more from merit than fashion.

Strangely enough, if you want to make something that will appeal to future generations, one way to do it is to try to appeal to past generations. It"s hard to guess what the future will be like, but we can be sure it will be like the past in caring nothing for present fashions. So if you can make something that appeals to people today and would also have appealed to people in 1500, there is a good chance it will appeal to people in 2500.

GOOD DESIGN SOLVES THE RIGHT PROBLEM. The typical stove has four burners arranged in a square, and a dial to control each. How do you arrange the dials? The simplest answer is to put them in a row. But this is a simple answer to the wrong question. The dials are for humans to use, and if you put them in a row, the unlucky human will have to stop and think each time about which dial matches which burner. Better to arrange the dials in a square like the burners.

A lot of bad design is industrious, but misguided. In the mid twentieth century there was a vogue for setting text in sans-serif fonts. These fonts are closer to the pure, underlying letterforms. But in text that"s not the problem you"re trying to solve. For legibility it"s more important that letters be easy to tell apart. It may look Victorian, but a Times Roman lowercase g is easy to tell from a lowercase y.

Problems can be improved as well as solutions. In software, an intractable problem can usually be replaced by an equivalent one that"s easy to solve.

Physics progressed faster as the problem became predicting observable behavior, instead of reconciling it with scripture.

GOOD DESIGN IS SUGGESTIVE. Jane Austen"s novels contain almost no description; instead of telling you how everything looks, she tells her story so well that you envision the scene for yourself. Likewise, a painting that suggests is usually more engaging than one that tells. Everyone makes up their own story about the Mona Lisa.

Figure 9-1. 1973 Porsche 911E.

In architecture and design, this principle means that a building or object should let you use it as you want: a good building, for example, will serve as a backdrop for whatever life people want to lead in it, instead of making them live as if they were executing a program written by the architect.

In software, it means you should give users a few basic elements that they can combine as they wish, like Lego. In math it means a proof that becomes the basis for a lot of new work is preferable to one that was difficult, but doesn"t lead to future discoveries. In the sciences generally, citation is considered a rough indicator of merit.

GOOD DESIGN IS OFTEN SLIGHTLY FUNNY. This one may not always be true. But Durer"s engravings and Saarinen"s Womb Chair and the Pantheon and the original Porsche 911 all seem to me slightly funny. G.o.del"s incompleteness theorem seems like a practical joke.

I think it"s because humor is related to strength. To have a sense of humor is to be strong: to keep one"s sense of humor is to shrug off misfortunes, and to lose one"s sense of humor is to be wounded by them. And so the mark-or at least the prerogative of strength is not to take oneself too seriously. The confident will often, like swallows, seem to be making fun of the whole process slightly, as. .h.i.tchc.o.c.k does in his films or Bruegel in his paintings (or Shakespeare, for that matter).

Good design may not have to be funny, but it"s hard to imagine something that could be called humorless also being good design.

GOOD DESIGN IS HARD. If you look at the people who"ve done great work, one thing they all seem to have in common is that they worked very hard. If you"re not working hard, you"re probably wasting your time.

Hard problems call for great efforts. In math, difficult proofs require ingenious solutions, and these tend to be interesting. Ditto in engineering.

When you have to climb a mountain you toss everything unnecessary out of your pack. And so an architect who has to build on a difficult site, or a small budget, will find that he"s forced to produce an elegant design. Fashions and flourishes get knocked aside by the difficult business of solving the problem at all.

Not every kind of hard is good. There is good pain and bad pain. You want the kind of pain you get from going running, not the kind you get from stepping on a nail. A difficult problem could be good for a designer, but a fickle client or unreliable materials would not be.

In art, the highest place has traditionally been given to paintings of people. There"s something to this tradition, and not just because pictures of faces press b.u.t.tons in our brains that other pictures don"t. We are so good at looking at faces that we force anyone who draws them to work hard to satisfy us. If you draw a tree and you change the angle of a branch five degrees, no one will know. When you change the angle of someone"s eye five degrees, people notice.

When Bauhaus designers adopted Sullivan"s "form follows function," what they meant was, form should follow function. And if function is hard enough, form is forced to follow it, because there is no effort to spare for error. Wild animals are beautiful because they have hard lives.

GOOD DESIGN LOOKS EASY. Like great athletes, great designers make it look easy. Mostly this is an illusion. The easy, conversational tone of good writing comes only on the eighth rewrite.

In science and engineering, some of the greatest discoveries seem so simple that you say to yourself, I could have thought of that. The discoverer is ent.i.tled to reply, why didn"t you?

Some Leonardo heads are just a few lines. You look at them and you think, all you have to do is get eight or ten lines in the right place and you"ve made this beautiful portrait. Well, yes, but you have to get them in exactly the right place. The slightest error will make the whole thing collapse.

Line drawings are in fact the most difficult visual medium, because they demand near perfection. In math terms, they are a closed-form solution; lesser artists literally solve the same problems by successive approximation. One of the reasons kids give up drawing at age ten or so is that they decide to start drawing like grownups, and one of the first things they try is a line drawing of a face.

In most fields the appearance of ease seems to come with practice. Perhaps what practice does is train your unconscious mind to handle tasks that used to require conscious thought. In some cases you literally train your body. An expert pianist can play notes faster than the brain can send signals to his hand. Likewise an artist, after a while, can make visual perception flow in through his eye and out through his hand as automatically as someone tapping his foot to a beat.

When people talk about being in "the zone," I think what they mean is that the spinal cord has the situation under control. Your spinal cord is less hesitant, and it frees conscious thought for the hard problems.

GOOD DESIGN USES SYMMETRY. Symmetry may just be one way to achieve simplicity, but it"s important enough to be mentioned on its own. Nature uses it a lot, which is a good sign.