He chuckled. Why is it that you knock on wood? I grinned.

I was expressing affection for one of Henry Mencken's favorite speakeasies.

This place dates back that far? I nodded.

It figures, he said. You've got this thing for the past, or against the present. I'm never sure which.

Maybe a little of both, I said. I wish Mencken would stop in. I'd like his opinion on the present ... What are you doing with it?

What?

The present. Here. Now.

Oh. He spotted the waitress and ordered a beer. Business trip, he said then. To hire a consultant.

Oh. How is business?

Complicated, he said, complicated.

We lit cigarettes and after a while his beer arrived. We smoked and drank and listened to the music.

I've sung this song and I'll sing it again: the world is like an untempoed piece of music. Of the many changes which came to pass during my lifetime, it seems that the majority have occurred during the past few years. It also struck me that way several years ago, and I'd a hunch I might be feeling the same way a few years hence, that is, if Don's business did not complicate me off this mortal coil or condenser before then.

Don operates the second-largest detective agency in the world, and he sometimes finds me useful because I do not exist. I do not exist now because I existed once at the time and the place where we attempted to begin scoring the wild ditty of our times. I refer to the world Central Data Bank project and the fact that I had had a significant part in that effort to construct a working model of the real world, accounting for everyone and everything in it. How well we succeeded, and whether possession of the world's likeness does indeed provide its custodians with a greater measure of control over its functions, are questions my former colleagues still debate as the music grows more shrill and you can't see the maps for the pins. I made my decision back then and saw to it that I did not receive citizenship in that second world, a place which may now have become more important than the first. Exiled to reality, my own sojourns across the line are necessarily those of an alien guilty of illegal entry. I visit periodically because I go where I must to make my living ... That is where Don comes in. The people I can become are often very useful when he has peculiar problems.

Unfortunately, at that moment, it seemed that he did, just when the whole gang of me felt like fuming down the volume and loafing.

We finished our drinks, got the bill, settled it.

This way, I said, indicating the rear door, and he swung into his coat and followed me out.

Talk here? he asked, as we walked down the alley.

Rather not, I said. Public transportation, then private conversation.

He nodded and came along.

About three-quarters of an hour later we were in the saloon of the Proteus and I was making coffee. We were rocked gently by the Bay's chill waters, under a moonless sky. I'd only a pair of the smaller lights burning. Comfortable. On the water, aboard the Proteus, the crowding, the activities, the tempo, of life in the cities, on the land, are muted, slowed, fictionalized, by the metaphysical distancing a few meters of water can provide. We alter the landscape with great facility, but the ocean has always seemed unchanged, and I suppose by extension we are infected with some feelings of timelessness whenever we set out upon her. Maybe that's one of the reasons I spend so much time there.

First time you've had me aboard, he said. Comfortable. Very.

Thanks ... Cream? Sugar?

Yes. Both.

We settled back with our steaming mugs and I asked, What have you got?

One case involving two problems, he said. One of them sort of falls within my area of competence. The other does not. I was told that it is an absolutely unique situation and would require the services of a very special specialist.

I'm not a specialist at anything but keeping alive.

His eyes came up suddenly and caught my own.

I had always assumed that you knew an awful lot about computers, he said.

I looked away. That was hitting below the belt. I had never held myself out to him as an authority in that area, and there had always been a tacit understanding between us that my methods of manipulating circumstance and identity were not open to discussion. On the other hand, it was obvious to him that my knowledge of the system was both extensive and intensive. Still, I didn't like talking about it. So I moved to defend.

Computer people are a dime a dozen, I said. It was probably different in your time, but these days they start teaching computer science to little kids their first year in school. So sure, I know a lot about it. This generation, everybody does,

You know that is not what I meant, he said. Haven't you known me long enough to trust me a little more than that? The question springs solely from the case at hand. That's all.

I nodded. Reactions by their very nature are not always appropriate, and I had invested a lot of emotional capital in a heavy-duty set. So, Okay, I know more about them than the school kids, I said.

Thanks. That can be our point of departure. He took a sip of coffee. My own background is in law and accounting, followed by the military, military intelligence, and civil service, in that order. Then I got into this business. What technical stuff I know I've picked up along the way, a scrap here, a crash course there. I know a lot about what things can do, not so much about how they work. I did not understand the details on this one, so I want you to start at the top and explain things to me, for as far as you can go. I need the background review, and if you are able to furnish it I will also know that you are the man for the job. You can begin by telling me how the early space-exploration robots worked, like, say the ones they used on Venus.

That's not computers, I said, and for that matter, they weren't really robots. They were telefactoring devices.

Tell me what makes the difference.

A robot is a machine which carries out certain operations in accordance with a program of instructions. A telefactor is a slave machine operated by remote control The telefactor functions in a feedback situation with its operator. Depending on how sophisticated you want to get, the links can be audiovisual, kinesthetic, tactile, even olfactory. The more you want to go in this direction, the more anthropomorphic you get in the thing's design.

In the case of Venus, if I recall correctly, the human operator in orbit wore an exoskeleton which controlled the movements of the body, legs, arms, and hands of the device on the surface below, receiving motion and force feedback through a system of airjet transducers. He had on a helmet controlling the slave device's television camera, set, obviously enough, in its turret, which filled his field of vision with the scene below. He also wore earphones connected with its audio pickup. I read the book he wrote later. He said that for long stretches of time he would forget the cabin, forget that he was at the boss end of a control loop, and actually feel as if he were stalking through that hellish landscape. I remember being very impressed by it, just being a kid, and I wanted a super-tiny one all my own, so that I could wade around in puddles picking fights with microorganisms.

Why?

Because there weren't any dragons on Venus. Anyhow, that is a telefactoring device, a thing quite distinct from a robot.

I'm still with you, he said, and Now tell me the difference between the early telefactoring devices and the later ones.

I swallowed some coffee.

It was a bit trickier with respect to the outer planets and their satellites, I said. There, we did not have orbiting operators at first. Economics, and some unresolved technical problems. Mainly economics. At any rate, the devices were landed on the target worlds, but the operators stayed home. Because of this, there was of course a time lag in the transmissions along the control loop. It took a while to receive the on-site input, and then there was another time lapse before the response movements reached the telefactor. We attempted to compensate for this in two ways: the first was by the employment of a single wait-move, wait-move sequence; the second was more sophisticated and is actually the point where computers come into the picture in terms of participating in the control loop. It involved the setting up of models of known environmental factors, which were then enriched during the initial wait-move sequences. On this basis, the computer was then used to anticipate short-range developments. Finally, it could take over the loop and run it by a combination of 'predictor controls' and wait-move reviews. It still had to holler for human help, though, when unexpected things came up. So, with the outer planets, it was neither totally automatic nor totally manual, nor totally satisfactory, at first.