Is Causation Extensional?

It is widely assumed that causation is an extensional relation: if c causes e and c = d, then d causes e. Similarly, if c causes e and e = f, then c causes f. Moving to the formal mode we have: The Extensionality Thesis (ET): (i) If „c causes e‟ is true and „c‟ and „d‟ co-refer, then „d causes e‟ is true; and (ii) If „c causes e‟ is true and „e‟ and „f‟ co-refer, then „c causes f‟ is true