Identity as a Process

Returning to a topic I've thought about before: identity is a problem.

I expect that most of you to be familiar with the "my grandfather's axe/boat/knife..." problem. In short, how does the identity of a composite object vary (or not) as the identities of the components vary? One proposed solution is the so–called perdurantist approach which hinges on the observation (at once both banal and deeply challenging) that what we think of as objects in the world are really structures with extent in three spacial and one temporal dimension (pace Kaluza-Klein type arguments). We don't seem to be very good at that sort of thinking. Note that perdurantism seems still to be talking about fixing the boundaries of a thing in order to identify it. I think that's missing a trick.

This [pdf] (via Michael Feathers) is a treatment of that trick I've not seen before.

In that paper the biological concept of autpoiesis (and the complex of ideas around it) is used to analyse the working of the glider pattern in Conway's Game of Life. I read the paper as telling us that identity of a glider is extent of the continuation of the process which at any given time looks to us like a glider.

Now, how to apply this understanding elsewhere...


mfeathers said...

It's odd. The first thing I thought of was Rich Hickey's talk at QCon where he was circling around a concept of "entity" in functional programming. If you don't have identity in the object sense (a durable referenceable object) you do have it in the sense that you have a process which produces a succession o values which seem to possess an identity if you de-focus your eyes a bit.

keithb said...


I think of the functional approach as having what we might call "duck identity": if it walks like this duck and talks like this duck then it is this duck. There might "be" (in some sense) one, or two, or ten or a million ducks known to the implementation, but the running program (in some sense) cannot distinguish that.

Paul W. Homer said...

There are a couple of great quotes from "A Short History of Nearly Everything", written by Bill Bryson that I used in a post a while back:

People, the quotes imply, are really just a cloud of related cells and bacterium that are (possibly) renewed every nine years.

If we accept 'identity' as only a tag that is attached to some constantly changing entity, then the only real difficulty is in choosing sides during a balanced split (which more often then not is actually the end of the entity).

The ship is the same ship, so long as everybody refers to it as the same ship. The 'ship' itself is a cloud of particles that is constantly growing and shrinking over time.

keithb said...

@ Paul: I think we get distracted by the rather slow (to us) pace with which substances move through most of the "unities" that we are able to distinguish.

Our bodies are in a continuous state of flux, certainly. Material and energy and information flow in, and flow through and flow out, all over us and all the time. We seem to be built not to pay proper attention to the ramifications of that without extraordinary effort.

Immo H√ľneke said...

This discussion brings to mind two thoughts:

1. Many individuals have more than one identity and use these for different purposes. Particularly online.

2. When I was in the ATC, a common joke about the RAF's heavy transport, the C130 Hercules, was that it consisted of 20,000 rivets in close formation...