For all things, for all locations y, for all locations z and for all times t, that a thing is in location y at time t and that y is not identical to z logically implies that that thing is not in location z at time t.

(∀x)(∀y)(∀z)(∀t)((Lxyt∧x≠y)⇒¬Lxzt)

Idea

The principle is meant to capture the common sense idea that if something is somewhere, then it is not somewhere else. It cannot be two places at one:

(∀x)(∀y)(∀z)(∀t)¬◊(Lxyt∧Lxzt∧x≠y)

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