I'm not sure what to call this sort of prepositional phrase, but this sort seems to interrupt the thought to add clarification. I almost want to call it an interjectional prepositional phrase.
- Are we not in principle taking a risk?
- Are we not, in principle, taking a risk?
- You in full knowledge allow discrimination to go unquestioned.
- You, in full knowledge, allow discrimination to go unquestioned.
So is it permissible and/or preferable to use commas in this situation?