American traditions and the American ethic require us to be truthful, but the most important reason is that truth is the best propaganda and lies are the worst. To be persuasive we must be believable; to be believable we must be credible; to be credible we must be truthful. It is as simple as that.

Great pretenses win nothing. The tears, the unctuous oratory — all are useless if, at last, we have no credibility. To win, we must be believed. To be believed, we must be believable. To be believable, we must tell the truth, the truth about ourselves — the whole truth.

Our first task therefore must be to persuade people.

To know, you just have to know. To believe, you have to make others believe.

He who wants to persuade should put his trust not in the right argument, but in the right word. —

“We must say the truth”.

The truth can be useful, sometimes. Assuming you can convince people.

You should be convinced of the authenticity of what you have, but you must also be humble enough to say that we don't know everything. And since we don't know everything, we must accept that another person may believe something else.

in order to succeed, we must first believe that we can.

We know how to tell many believable lies,
But also, when we want to, how to speak the plain truth.

What convinces is conviction. You simply have to believe in the argument you are advancing; if you don’t, you’re as good as dead. The other person will sense that something isn’t there.

What’s important is to stick to our principles, be honest, be active, be articulate, be reliable.

First we have to believe, and then we believe.

It is a principle of diplomacy that one must know something of the truth in order to lie convincingly.