Strength of Obligations

In certain deontic arguments, particularly in deontic analogues of modus ponens, at least two premisses and the conclusion are obligation statements. Now obligations vary in strength. Does then the strength of obligation in the premisses of such an argument determine the strength of obligation of the conclusion? I consider and reject three positive answers to this question. I opt for a negative answer: Any belief that strength of obligation carries over from premisses to conclusion is a feature of the pragmatics, not the logic, of obligation-talk.