In Act IV, Scene III of Shakespeare’s “The Tragedy of Macbeth,” Malcolm tells Macduff that even someone who has morals and integrity may cave under the pressure of a demand from their king. Malcolm is referring to Lucifer (the Devil.) In most religious traditions, Lucifer is considered the most intelligent (the brightest as in genius) and the most outstanding (the brightest or best) of God’s angels. In addition, Malcolm is saying that Macbeth was once the brightest and best and now he acts a lot like Lucifer.
Have you ever heard someone make the statement, "That's beyond the pale!" and wondered what the phrase actually means? There are books, blogs, and musical lyrics that include this phrase, yet none truly reflect its meaning. The answer is lies in Irish history and is fairly complex.
Essentially, to “cast pearls before swine” is to share something of value with those who cannot appreciate it.