What does the sentenc mean? Thank you all. Thank you all for your kindness. The sentence is from In Favor of Capital Punishment written by Jacques Barzun. The whole sentence is "If psychiatry were sure of its ground in diagnosing the individual case, a philosopher might consider whether such dangerous obsessions should not be guarded against by judicial homicide 'before' the shooting starts." Particularly, I don't understand what "should not be guarded against" means