> I've had this sneaking but hard to articulate suspicion that datacenters, bare metal servers, VMs, operating systems, containers, OS processes, language VMs, and threads are all really attempts to abstract the same thing.

There is a very easy way to articulate it: they are all ways of virtualizing different facilities. Unix processes virtualize the user-mode processor registers and the address space. POSIX threads only virtualize the processor registers and the stack. Linux namespaces let you pick and choose which facilities you want to virtualize (storage, PID namespace, IPC namespace, etc.).

The abstraction is related to what is being virtualized: everything that is virtualized is a namespace (this is what naming things refers to in Phil Karlton's quote "There are only two hard things in Computer Science: cache invalidation and naming things," not to the literal naming of variables in computer programs).

Another way to go instead of virtualization is capabilities.