Whenever you say something, and later, whenever you think something,…you have to feel into the body, as to whether it is true or not…the body is closely connected with the past bhavanga and vibrating bhavanga …your first measuring stick might be only as to whether your energy body is straight or whether it contains many knots and twists…perceiving many knots and twists, you will know, that you can not trust your mind…but becoming aware thus,…you will equally also become aware of what you will have to do in order to become independent at some stage in the future.
As a persons meditation improves, he will build into his body and thus life-continuum, mechanisms, which inform him as to the truth of something…with that, he will learn to perceive the truthfulness of something, or the lack thereof…he will learn to connect through the tool of his body, all lies and all things that do not accord with his better knowledge with painful feelings,… and he will equally learn to connect truth and honesty and Dhamma with pleasant feelings… This, so he slowly starts to understand, is the way to independence from externals, the way towards unshakable freedom. And these mechanisms are what is called conscience.
Higher Mind Art - Abhidhamma Explorations 