No loopholes
Lying, according to this position, is the ultimate slippery slope. First, because a liar has to expend infinite amounts of energy just keeping his stories straight. You start out telling your neighbor that the IPod player he wanted to borrow for his party is broken, and then you have to maintain the lie by not letting him see you using the IPod. You also have to make sure your wife knows not to let on.
Already, your lie has cost you energy. And there is always danger that it will be exposed in the future, after which your neighbor will never really believe or trust you. Not to mention your wife, who’s probably already heard you lying about other stuff. The other argument for radical truthfulness goes much deeper: lying takes you out of alignment with reality.
This was Gandhi’s position, based on the insight that truth lies at the very heart of existence, of reality. A kabbalistic text calls truth ‘the signet ring of God,’ while the Taitteriya Upanishad says that God is truth itself. In psychological terms, since lying disconnects us from reality, it will always make us a little bit crazy. Anyone who grew up in a family that hid secrets will recognize the feeling of cognitive dissonance that arises when facts are concealed.