Geach Axiom
Modal logic axiom extending S4. Gives you the light-cone - i.e. causal arrows between points in space-time. prefix=van, p97, is where I first came across it; proved in Goldblatt
Modal logic axiom extending S4. Gives you the light-cone - i.e. causal arrows between points in space-time. prefix=van, p97, is where I first came across it; proved in Goldblatt