A train provides an isolation for the world, but it’s also many worlds inside. Each compartment often isolate itself from interaction. We sit accustomed to each other, neglecting the rest of the train, and they are visible like shadows passing a frosted glass. I think that Plato would have said that this is how we see reality all the time. Suddenly the door opens and the train conductor says: OMSK, and once again a window opens to reality.

Sliding doors to another world open and close without my intention

Picture from Wikimedia Commons