The syntax is `<pip> install "<package><comparison><version>"`, so in this case 'pip install "Sphinx==1.3.6"` (or `pip install "Sphinx<1.4"`) should do it for you.  That ought to also take care of downgrading any other packages that need it (though I don't think there are any), or at least tell you which ones should be downgraded and to what.

I'm not sure why there are both `pip list` and `pip freeze`, but `pip freeze` is the one that outputs usable syntax for a requirement specifier.