“For slaves no freedom have, not e’en in speech.”

And again:–

“You’re but a slave, and may not dare to speak.”

(49) As, therefore, musical science gives to all those who have studied music an equal right to speak on matters connected with their art; and as a man who is learned in grammar or in geometry has a right to speak among grammarians and mathematicians, so also the law in life allows the same privilege to those who are learned in the way in which men ought to live. (50) But all virtuous men are skilful in all the affairs which belong to life, inasmuch as they also are so with respect to the things which belong to universal nature; and some of them are free; and so therefore are they who have the freedom of speaking to them on equal terms; therefore no virtuous man is a slave, but all are free.