Earlier quoted context omitted.
We don't. But we also don't know that they were, and we don't have enough quality evidence in favor of that hypothesis to justify the confidence with which it is asserted. In the absence of evidence about the timing being affected by other festivals and in the presence of much evidence that all the actual traditions are far more recent than pagan, I don't believe it's fair to claim Christmas has pagan origins. The ab…
I agree but I also would be interested to see any proof for the claims you're talking about with regards to Christmas not having any pagan roots, where are you finding this information or rather, where can I read more?
Here's another one on Saturnalia from the same scholar: