Andrew Critch, March 2023:
By boundaries, I just mean the approximate causal separation of regions in some kind of physical space (e.g., spacetime) or abstract space (e.g., cyberspace). Here are some examples from my «Boundaries» Sequence:
- a cell membrane (separates the inside of a cell from the outside);
- a person's skin (separates the inside of their body from the outside);
- a fence around a family's yard (separates the family's place of living-together from neighbors and others);
- a digital firewall around a local area network (separates the LAN and its users from the rest of the internet);
- a sustained disassociation of social groups (separates the two groups from each other)
- a national border (separates a state from neighboring states or international waters).