Tips for Use. That many speak nonsense or don’t know what they are talking about requires no explanation or proof. Turn on any TV channel and masochistically listen to the typical declarations of sundry politicians. Generalities, platitudes, untruths, statements of fact unsupported by evidence… you choose.
But the same applies (often) to situations you may encounter at the office in an almost endless number of occasions. “This is senseless speaking or a speaking such as sense cannot untie” is an elegant but sharp arrow targeted at the incompetence (or arrogance) of your stupid political enemy. Much better than the overused “This is BS” or similar. You will acquire points with those who may listen to the exchange or debate. In the book “Your Daily Shakespeare” you will find literally hundreds of pointed and effective lines to “drive your enemies into despair.”
In the play. The valiant Posthumus Leonatus, has joined the English forces in a battle against the Romans and valiantly helped defeated them. However, since he was also a Roman as well as an Englishman, he has been jailed and condemned to die. Depressed in his cell, he has a dream foretelling that his fortunes will brighten. He is, however, skeptical and does not understand what he is told in the dream. Hence his comment.