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

[polymath257]

Go ahead, give me one example of something you can conceive of, and which is logically impossible to exist at the same time.

And more importantly for this thread, I can conceive of an infinite regress of causes. According to you, that is logically impossible (even though it is trivial if the  sequence of causes is indexed by the negative integers).