Over at Dangerous Idea, the only reasonable counterargument was that the spaces of reductionist physical worlds and of god-created worlds are both infinite space, and that, as a result, we couldn't compare them. (There were plenty of unreasonable counterarguments, but I won't go into them here.)
So, to revise my argument, I'll consider something quite specific to our own universe. Consider the following spaces:
- The space of designed life-bearing worlds that have the physics of our universe.
- The space of non-designed life-bearing worlds that have the physics of our universe.
Obviously, the first space is vastly larger than the second. To begin with, there is no need for a god-designed life form to even be consistent with the physics of our universe. There is no need for descent, common descent or common composition. And for every collection of species on a planet, there are countless variations that a god could design that are unreachable by unguided evolution.
This argument is essentially the same as before, but now the space of physical configurations is finite (albeit large). The space of god-designed variations is vastly greater, and quite possibly infinite.
Evolutionary biology may be neutral on the question of whether a god exists, but it is most certainly not neutron on the question of whether life was intended or designed. Given the facts of biology, it is irrational to believe life was designed.