If we have an idea that we do not communicate it never leaves our mind. The whole mind is the source of ideas. If we communicate an idea but it is not understood it never leaves its source. So our understanding makes a copy of the idea and our words communicate the idea into the minds of others when we explain it. If those with whom we share the idea lack understanding then our idea will not be fully realised. We do not need to understand an idea for it to control or influence what we think or feel. Without understanding we can be conditioned to compliantly behave or respond.