I'm a little suspicious of people who claim to think "everything" through from "first principles" (whatever those are).
Where do you get your first principles from?
If you get them from observing the world around you, how do you decide what parts to pay more or less attention to?
While you're deciding things from first principles (and coming up with those first principles), how do you make decisions in the mean time?
Note that in physics, computing things "from first principles" is often done to attempt to recreate a result that's already been reached by other approaches, to attempt to verify that you've got the right set of first principles.
Where do you get your first principles from?
If you get them from observing the world around you, how do you decide what parts to pay more or less attention to?
While you're deciding things from first principles (and coming up with those first principles), how do you make decisions in the mean time?
Note that in physics, computing things "from first principles" is often done to attempt to recreate a result that's already been reached by other approaches, to attempt to verify that you've got the right set of first principles.