Pater Noster for Non-Believers

Our Father, if you exist, I dare to turn to you.
If you exist, your name is holy: may it be sanctified.
If you exist, your kingdom is order, and likewise it's splendor: may your kingdom come.
If you exist, your will is the law of the world and the law of souls: may your will be done in all of us in everything, on earth as it is in heaven.

Give us, if you exist, our daily bread, the bread of truth, the bread of wisdom, the bread of joy, the super-substantial bread which is promised to those who can recognize it.
If you exist, I have great debts towards you: grant that I will repay my debts, as I would willingly have myself repaid by those who owe me.
In the future, do not abandon me to temptation, but deliver me from every evil...

...The atheist has an obligation to pray thus. One may doubt; but can that sincere soul, going to the depths of his very being, with certitude, deny God? The conditional prayer is therefore an obligation and at the same time an useful appeal.

"Le Pater de L'Incroyant"
Catéchisme des Incroyants, Vol. 1, A.-D. Sertillanges, O.P. Flammarion: Paris, 1930, p. 6.

Plinthos translation.