children and fools tell the truth
Children and fools do not know that lying can sometimes be useful, helpful, or preferable to the truth. A: "I was mortified when my son told that woman her hairstyle was ugly." B: "Well, children and fools tell the truth."
Children and fools tell the truth.
Prov. Children have not yet learned, and fools never did learn, that it is often advantageous to lie. Fred: What will I tell Ellen when she asks why I'm so late getting home? Alan: Tell her the truth—we were out having a few drinks. Fred: Children and fools tell the truth, Alan.