The words used in direct orders are the only ones about which we can be sure that they are efficient.
It can be supposed that the birth of language was caused by the need of giving orders.
And maybe there is right to say that our actual long speeches which claim to be communicative or to share information with others conceal in fact the desire of giving orders.
When we keep silence and speak only to ourselves, it would be a way of giving orders to us. We easily accept to receive orders from ourselves, so that the words we silently speak prove to be more efficient than those we address to others.
So efficient they are, that we become enclosed in our inner discourses. Therefore, we cannot be something else than our words and we forget the habit of using them for deceiving our intentions of giving orders. In this way, the silence teaches us the sincerity. But such sincerity is not well received by other people, who are rather accustomed to be gently lied.