At some level one can think of anything as unique, but it's often more useful to consider in what way two (or many) things are similar. We've got a bit of a di

At some level one can think of anything as unique, but it's often more useful to consider in what way two (or many) things are similar. We've got a bit of a dialectic: Thesis -- The map is not the territory. Antithesis -- There's nothing so practical as a good theory. Synthesis -- Use a subway map when catching the train, use a topographical map when doing flood planning, etc. Taking it back to programming, all abstractions are leaky in some way. A good software engineer uses the right abstraction for the task, knowing that it might be wrong for a different task.