In philosophy, a causal chain is an ordered sequence of events in which any one event in the chain causes the next. Some philosophers[who?] believe causation relates facts, not events, in which case the meaning is adjusted accordingly.
Some philosophers[who?] believe that causality may not exist if determinism is true, as causality is merely the observation that one event precedes another, or that there is a pattern throughout spacetime in which events of one similar type tend to correlate with events of another similar type (that is, the mass-energy distribution in spacetime has an information theoretic 'pattern' where car crashes tend to be correlated with injury, say). There may be no ultimate reason for why a chain of causality occurs the way that it does beyond the fact that a chain of causality exists. The fact that certain events seem to 'cause' other events is the recognition of a pattern in the structure of spacetime and the mass-energy that exists in spacetime, which is ultimately either due OR an instantiation of the laws of physics. Note: Stating that causality does not exist may be a bit misleading, as one would have to Define what is meant by 'causality' - it may be that causality is dependent upon counterfactual definiteness, that is, A causes B because, if A did NOT occur, then B would not occur (i.e.: A is necessary for B) AND because A is sufficient for B. It may be possible that causality is ultimately a meaningless concept (if one rejects counterfactual definiteness for instance), but that causal chains are still a valid concept (as they would merely be chains of events).