Gerry Sussman on Biological Systems

Yesterday, I lamented that our computer systems are so short-lived, as opposed to biological systems (like humans) which routinely live lives twice as long as the longest-lived computer system.

I want to be clear that I am talking about the uptime/runtime of a mostly static system, not something like UNIX that is constantly maintained (unless there’s a 3B2 in Bell Labs somewhere running UNIX from the 70’s processing payroll or something).

I was reminded about this talk from Gerry Sussman titled We Really Don’t Know How to Compute.

My main takeaway has to do with types and correctness. Basically, that they are a dead-end. They are very useful (I use them!), but correctness isn’t an interesting goal for a long-lived system.

Sussman brings up biology—and one point he stresses is adaptability.

If adaptability is a key to long-livedness, then type-systems and correctness appear to be in opposition to that. As do runtime assertions. Imagine if humans “crashed” if they got unexpected input. Or what if humans simply refused to “boot” if they had a minor gene “incorrectness” (admittedly, they do refuse to boot with major gene defects).

Here’s an example of adaptivity in humans: we take food as input. We were designed by evolution to use whole plants and maybe some meat as optimal fuel.

However, a modern human can live on processed food, much more meat and dairy, oils, refined sugar, and many things that did not exist when we were designed. We don’t crash immediately on that input or even reject it. We get fat, we develop heart-disease, diabetes, etc.

In other words, we get feedback that the input is bad—eventually the system will end earlier than it would have with better input, but there are many examples of long-lived humans that have never had perfect input.

Is the Human system “correct”? How would you use Domain Driven Design and types to describe the input to this system?

The reality is that the input is essentially infinite and unknown, and what matters more is the adaptability and feedback.

Gerry’s talk has something to say about what kind of programming language you need for this (Spoiler Alert: Scheme), but generally more dynamic, more data-driven languages will work better.