The odds of your unlikely existence were not infinitely small
“But there’s a fun, important, and underappreciated consequence of Bayes’ theorem that can tell us something vital about any of these steps: the odds of any one of them happening, no matter how small, could not have been infinitesimal. If you want to create our Universe with our laws of physics, our local group, our Sun, our Earth, and every one of us, given all the conditions that existed before the Big Bang, that probability may be very, very small, but it can’t be infinitely small. If it were, our model for the conditions that existed before the Big Bang could be ruled out immediately, with no need to gather data or make measurements.”
There are a great many events that occurred to give rise to the world, the Universe, and you. Everything from the Big Bang to the existence of the laws of physics to the cosmic history that created Earth to the biological history that gave rise to the 7+ billion of us today needed to unfold exactly as it did in order for things to be the way they are today. It’s an exceedingly unlikely story, and yet the fact that we’re here is evidence that it happened exactly in this fashion. But no matter how unlikely it appears, we can be 100% certain that our arrival at this point in time with these exact conditions wasn’t infinitely unlikely. In fact, it’s an inescapable consequence of Bayes’ theorem that the existence of things as they are today implies it had a finite, not infinitesimal, probability of turning out this way.