The a Priori Argument for the Universe Began to Exist

There seems to be the case that when something begins, it seems as though there'd be some sort of prior condition. And so arguably this is perfectly compatible with quantum mechanics. So why should we think this? Well, you could go kind of a posteriori support. In that case, you'd be looking at maybe something like Big Bang cosmology or maybe the Board of Goods for Lincoln's Erum. That would allow us to conclude that the past cannot be infinite and therefore universe has a beginning.