I hope Steve Kline is remembered, not only for the things he did, but for the special way he did them. Steve Kline was a person of vision. So are we all. But Steve's commitments to vision were specially intense, and specially disciplined. I hope some sense of Steve Kline's commitment to human vision can be remembered, and can guide us. Pictures are hard. A young child can often respond with very clear words. Ask that child "draw me a picture" - see what you get. Ask an adult the same, and you'll often be appalled at how little detail the adult can actually construct and remember. Steve Kline wanted pictures, whenever he could get them. Images were part of his thinking. Steve liked abstractions all right, but he wanted abstractions that connected, in step-by-step graphical and pictorial detail, to things that he could SEE. I hope Steve is remembered for that special, careful, disciplined way of thinking.

In 1613, Galileo spoke of two kinds of "vision" - sensory vision "what the eye of the forehead" registers, and understanding "what the eye of the mind envisions." Steve Kline worked hard to connect the world that could be seen with his physical eyes, to useful systems of ideas in "the eye of the mind." Steve formed and judged ideas with the same concern for detail, the same desire for traceable connection between different points of view, that he applied to pictures.

Steve knew how hard it was to get ideas that correlated, step by step, with pictures, or graphs, or clean outlines. Difficult or not, that was his standard. Clear, fully connected patterns of ideas, explicitly matchable to tangible things could be CHECKED, and focused, and modified. For Steve, getting this clarity and consistency was an essential part of the creative process.

Steve Kline checked his own ideas against evidence all the time. He judged other people's ideas by the same incisive standards he used to judge his own. Sometimes, if he had a clear, meticulously checked image in his mind, and your image was less focused and less checked, he could be overwhelming. Often, though not always, he was also right.

The fluids profession owes a debt to Steve's forceful temperament, as well as his intellect. The idea had become dominant that turbulence WAS statistical. Forceful men said that flows were so complicated that you could "see anything you wanted in them." These people said that cause and structure ceased to be when flows became turbulent. Some statistical models described some data very well. The system seemed closed and complete, and sterile.

Over a period of about a decade, Steve and others showed data and presented ideas supporting a different notion. Turbulence could be thought of in differential and structural terms. Flow visualization, carefully done, DID show real patterns. Notions of causality and structure made sense in turbulence.

It is too stark, but still clarifying, to say that this was a fight between people who were for pictures, and people who were against them. This was a controversy between people who believed in pictorial detail, and the three dimensional complexity it could show, and people who believed in stark mathematical descriptions, stripped of pictorial content, where "football shaped correlations" were "all you ever knew, and all you needed to know." Steve stood on the side of pictorial detail.

It was a long hard fight for Steve and his side. Steve was shunned at some technical meetings, and it bothered him. Steve was laughed at by his main opponent in controversy, a powerful and funny man, whose jokes could stick and burn. Most of all, Steve remembered this. Steve cornered people with flow visualization pictures in meetings and said "see those spots?" "see those streaks?" People refused to look, or REFUSED TO ACKNOWLEDGE WHAT WAS BEFORE THEIR EYES. The problem wasn't boredom. Sometimes hands shook. This was a fight.

Steve and his colleagues believed their eyes, and ideas that fit what they saw, and kept on. I'm glad.

So are many other people. Today, flows around whole airplanes are being modeled in computers. Today at Stanford, flow modeling of whole turbojet engines is well begun. Better airplanes and better flow machines of all kinds have already resulted, and more will come. This work would be unthinkable according to the older statistical model of turbulence.

Steve had some admirable but sometimes uncomfortable virtues. Steve Kline was absolutely sure that he could be wrong, and unashamedly sure that you could be, too. Steve was remarkably comfortable with the limits of his own understanding, and unashamedly certain that you had the same limits yourself. His tests of his rightness or yours, of his limits or yours, were stark pictorial standards, or as close to pictorial standards as he could get.

Steve Kline thought that the highest standards of description and understanding involved pictures, and words, and math, all fit together. The pictures and words and math had to be traceably related, step-by-step, with enough sharpness and enough cross-references for checking of many kinds.

Steve thought the documentation in manufacturing engineering was very good description. It had enough views that, with hard looking, one could see what was being described. It had enough words so that interactions were clear. It had enough numbers and mathematical relations for a sense of detailed proportion. Pictures, words, and numbers fit together. Steve worked to get his own ideas that clear, and that detailed, and that tightly fit to context.

If, sometimes, Steve seemed clearer than other people, it was because he was. He'd worked to be. Steve's conceptual images were crafted, checked, reworked, and worried over, like paintings, not rough sketches. Steve's conceptual images were vivid to him, and he could often make them seem real to others.

Steve Kline spent much of his career staring at flow patterns that he could not understand, and that nobody else understood, either. Lots of times, the patterns were not only too complicated to fit in his head, they wouldn't fit into a supercomputer. Steve worked hard to make connections that worked, and sometimes did. But often when he was working, he had to say "I don't understand" or "I can't make this fit" tens or hundreds of times a day. He achieved something rare - a matter-of-fact, comfortable sense of his own ignorance, and a matter-of-fact sense of what he had reason to believe.

Steve had a hard won, vivid sense of the boundary between where he understood and where he didn't. This gave him unusually clear judgments about what problems needed to be attacked, and what problems were ripe for attack. These were judgments that he could explain and justify to others. Some of those judgments made a difference.

Steve was not a man of religious faith, but he was a man of intense intellectual faith. Steve believed that reality was there, even if it was unseen. He believed the world was understandable in the end. Steve believed that by looking hard at problems, representing them more and more sharply, more and more starkly, and checking and rechecking logic and evidence, breakthroughs would be possible. Steve wanted to define and represent systems more and more sharply, more and more carefully, more and more meticulously, until details stood out that might offer clues to something new and useful. He taught his students to look harder, look longer, and look more meticulously than they'd naturally want to. Sometimes Steve's focus would exasperate and exhaust everyone around him. And yet, sometimes he'd be able to straighten something out, and solve difficulties, before the rest of us were even aware that there was a problem.

The connections between his fluids work and his socio-technical work were closer, Steve felt, than people thought. Steve's strongest commitment, in fluids, was to the notion of representation, the ideal of models that made detailed mathematical and observational sense. Steve felt that the first half of his book, CONCEPTUAL FOUNDATIONS owed an enormous amount to fluid mechanics, and addressed problems that had to be solved if certain kinds of progress in fluids modeling were to be possible. In the later part of his career, some people felt that Steve sometimes neglected the fluid sciences. So far as I could tell, Steve himself never felt that way. He was working on modeling problems that had to be cracked, to permit progress in fluids modeling, and to permit progress elsewhere, too.

I'll miss him very much.

If you would remember Steve Kline, look at your problems a little more sharply. Stare at them a little longer. Do more cross-checking. Make sure that what you see and what you say about it fit tightly. Worry more. Be a little more ready than you might otherwise be to discard an idea related to your problem, and try again. Keep at it. Sometimes you may gain new and important insights, as he did.

That would be Steve Kline's best memorial.