I think this is a design issue that is orthogonal to functional languages or static typing. We could easily create a language where writing "if foo" causes an error when foo doesn't resolve to an instance of Boolean. If we like, we could add coercion to boolean through the #to_b" method (although I have issues with implicit coercion).

At a deep level, I wonder if my issue is with if stamens and boolean operators being magic outside of the object system. Smalltalk gets this right. Scheme gets this right. if "if" is defined in the standard library rather than being magic syntactic construct, we can write our own control primitives:

    provided account = Account.create(params[:account])
      ...
    end

:-)