ABSTRACT
There clearly are basing prohibitions, and they satisfactorily explain the asymmetry. The opposite of a basing prohibition is a basing permission. In Broome ( 2014 ) I said that a permission is simply the negation of a prohibition. I meant that for something to be permitted by rationality is for it not to be prohibited. I now realize that was a mistake. My own account of requirement, which is presented in Broome ( 2014 ), means I have to allow for some things that are neither prohibited nor permitted. ‘Permitted’ is a narrower category than ‘not prohibited’. However, the distinction is technical and need not trouble us here.
