Qui tacet consentire videtur.
(Legal)

Pron = kwee TAH-ket kohn-sehn-TEE-ray wih-deh-toor.

He who is silent (about a thing) appears to give consent (to that thing).

Comment: While the source of this proverb is unknown, I think it might as well or even better be labeled "ethical" as "legal", for what is really at stake in this proverb are those things that we know about and say or do nothing about. Our silence both in word or deed is a sign of our consent, or at least our unwillingness to do anything to bring about a change. Our silence becomes passive agreement with the thing, however unpleasant we may say that it is.

Several things come to mind when I consider this proverb: the adult in any situation who knows that a child or minor is being abused (physically, sexually, verbally, emotionally) and says nothing; this is a deadly, life changing thing to be silent about. This silence happens every day, and children suffer. And, it is illegal to remain silent about such things.

Less about law and more about ethics: the conversation that goes around among "friends" about one who is not present. The conversation is disparaging and yet one remains silent who knows that the disparaging comments are not true, or are even not quite true, but says nothing.

These are two examples on opposite ends of a spectrum: both employ
silence as a response to what the listener knows is not acceptable.
The silence implies the listener's agreement with what is being said or done.

I have students right now who have become very interested in and activist about the tragedy that is Darfur. Yesterday one brought me information about a workshop that they want to go to. Do I think the
school would give them an excused absence to attend this workshop?
They will learn, among other things at the workshop, how to use their voices in the face of injustice. They will be joining hands with those who refuse to be silent in the face of injustice.

Holding hands always makes the voice stronger. I think Martin Luther King, Jr. and company learned that when they crossed the Gordon Pettus Bridge in Selma, AL--King who is often quoted quoting Ghandi--all that evil needs to flourish is for good men and women to do nothing. In other words, to remain silent and give evil their consent.