The Wikipedian on the left is not playing fair: he has two hidden cards behind his back.

Honesty is expected in all processes of Wikipedia, including content discussion, the dispute process and all other functions of the community. Editors are reminded that while you may expect an assumption of good faith, this is based on the counter-assumption of honesty in your actions.

Being honest does not mean being perfect. An honest Wikipedian may make honest, good faith mistakes.