Axioms

Axioms

That's right.

Let me quote Leslie Lamport, from the 1978 article cited by Paolo Bonzini:

This definition will appear quite natural to the reader familiar with the invariant space-time formulation of special relativity, as described for example in [1] or the first chapter of [2]. In relativity, the ordering of events is defined in terms of messages that could be sent. However, we have taken the more pragmatic approach of only considering messages that actually are sent. We should be able to determine if a system performed correctly by knowing only those events which did occur, without knowing which events could have occurred.

The references [1] and [2] are two introductory texts on relativity of those times.