Identity over time
Questions about what makes something persist through change — and an unexpected echo of them in software.
A seedling: questions rather than answers.
Things change but, we usually say, remain themselves. The Ship of Theseus is the classic stress test. Several candidate criteria for persistence are commonly discussed:
- Material continuity — the same stuff.
- Formal or structural continuity — the same arrangement, gradually maintained.
- Functional continuity — doing the same job in the same role.
An echo in software
Software has to answer a narrow version of the question constantly. When a request arrives twice, is it the same request or a new one with the same contents? Systems decide by fiat, assigning an identifier that defines sameness; see Idempotency, and Why Retries Need It.
That suggests a question worth tending: is identity sometimes less a fact we discover than a convention we choose, because some purpose needs one?