It's science. Such as from Einstein, who was a lot smarter than I am.

There are so many constraints necessary for a planet to form life of any type, such as how close the planet is to its sun to get the necessary energy, to be old enough to be cool enough, and more. Those are conditions put forward by a lot of scientists.

That formula claiming to predict millions of habitable planets was invented out of one man's head, and has no science behind it, just his "reasonable" assumptions. He pulled it out of his ass, and other scientists thought it was good.

So I believe the evidence is very conclusive.