The Sussman's take on /prog/'s SICP fan club

Your message was perhaps one of the strangest pieces of email I have ever received. Although it is flattering to have a ``fan club'', in fact, it is a very bad idea. Unlike most of human society, science and engineering are based on the idea that each of us is capable of evaluating evidence and thinking on our own. Each of us can do experiments, work out the reasoning, and determine the truth for ourselves. There is no room in science or engineering for ``fans'' representing group approval over individual thought. One of my heros, Galileo, put it very well:

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.

I am pleased to talk with people about matters of science or engineering, so you and your colleagues may certainly send me mail. I hope to learn as much from your experiences as you may learn for me. But please get rid of the ``cult of personality'' way of thinking. It is unscientific and ultimately destructive.

The Sussman is truly a king among men.

We Really Don't Know How to Compute!

Though we have been building and programming computing machines for about 60 years and have learned a great deal about composition and abstraction, we have just begun to scratch the surface.

A mammalian neuron takes about ten milliseconds to respond to a stimulus. A driver can respond to a visual stimulus in a few hundred milliseconds, and decide an action, such as making a turn. So the computational depth of this behavior is only a few tens of steps. We don’t know how to make such a machine, and we wouldn’t know how to program it.

The human genome — the information required to build a human from a single, undifferentiated eukariotic cell — is about 1GB. The instructions to build a mammal are written in very dense code, and the program is extremely flexible. Only small patches to the human genome are required to build a cow or a dog rather than a human. Bigger patches result in a frog or a snake. We don’t have any idea how to make a description of such a complex machine that is both dense and flexible.

New design principles and new linguistic support are needed. I will address this issue and show some ideas that can perhaps get us to the next phase of engineering design.