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...