Tip for Use. Answer or comment to an expression of amazement or incredulity. The second part of the quote, “All difficulties are but easy when they are known” may serve as an appropriate answer to the many experts who claim that their solution (to whatever problem) is ‘easy’, when in fact it is the opposite.
In the play. The Duke of Vienna (in disguise), is orchestrating a plot designed to unmask the hypocrisy of Angelo. The Duke reassures a somewhat puzzled prison provost who is skeptical.