Beatty uses many allusions in his defence of why books are so dangerous and why they have been eradicated from the society of this dystopian world. One of them is an allusion to Shakespeare's play, The Tempest, which reads: "A kind of excellent dumb discourse."
This quote actually comes from Act III scene 3 of Shakespeare's play, which is when Ariel creates a kind of pageant for Gonzalo, Alonso and Antonio to watch, and also provides them with food. Note the full quotation from Alonso:
Such shapes, such gesture, and such sound, expressing,
Although they want the use of tongue, a kind
Of excellent dumb discourse.
Prospero, watching Alonso saying this, responds very sarcastically to this remark, and when the context of Beatty's remarks is considered, there is irony in the use of this allusion too. Beatty is arguing that books creates a "kind of excellent dumb discourse" but the basis for his argument is a series of literary allusions that show the enduring quality and importance of literature for all generations. He is arguing for the destruction of books whilst appealing to books in order to support his argument.