If causality is a category of perception as Kant claims why are so many scientists unfazed intellectually by the claim that the Big Bang theory must be an incomplete theory of the universe because the existence of the big bang must have been caused by something prior to the big bang? Personally I side against the scientists in my firm belief that they are defying commonsense in their rejection of the idea that the existence of the universe at the time of the big bang must have had a prior cause. So scientists seem to be rejecting the idea that all occurrences have a cause.