Agreed; under uncertainly, you should shrink the size of your bet. For example, I think open borders might be good for the world (maybe outside of pandemics, s

Agreed; under uncertainly, you should shrink the size of your bet. For example, I think open borders might be good for the world (maybe outside of pandemics, say), with less than 100% confidence. However, debating completely open borders is sort of pointless. The actual lever we have is how much legal immigration we allow (and possibly how much enforcement we do against illegal immigration). So in practice, the road to open borders would be steady increases in the number of visas we grant (unless things start to go badly), not just tearing down the "fence" all at once.