The Principle of Contingent Causation: The Impossibility of Infinite Regress.

[polymath257]

Why would that be the case if there was no causal link? And, in fact, it is quite easy in a relativistic scenario, to have multiple events, even ordered in some reference frames, that have no causal links.

I'm simply going by the common definition that contingent things do not exist in all possible worlds but necessary things do.  Not that I have any love for any of these definitions as my general reaction to the notion of necessary existence is, "What does that even mean?"

Oh, I agree. The whole notion of 'contingent existence' and 'necessary existence' are deeply problematic to the  point of being meaningless.

I was simply  pointing out that relativity does NOT eliminate the possibility of multiple uncaused causes as long as they are all outside of the  light cones of the others. The fact that some would be 'before' others in certain frames of reference is irrelevant since there can be no causal connection.