Romans 1:20
Exactly - Christ said God is Life. I take that to mean the Animating Principle of the Universe - or that which tells Matter to get up and walk. That Principle is invisible - we know it by seeing it in action, but we quickly forget the totality, the unity of Him/It as we are enmeshed in Life, held to chains of cause and effect - instead we divide Him/It as food, friend, enemy, parent, child and so on. (May explain the Blessed Sacraments being ritualized eating, and why the Fall was depicted as an act of disobedient eating.)
Faith is impossible to use as an argument with an atheist, the stumblingstone is religion itself to many of them, that is, the various sects and the poor in spirit will never get it on the personal level until a trial is placed upon them they would rather not deal with alone. I’m old enough to have seen family atheists wither on into old age, too forlorn to accept any sort of guidance, bent on having it their own way to the end. Eventually they have cast aside the succor anyone else might offer and a sort of cowl of bitterness comes over them. Why share with Life anymore? Life is not compelling to them and they have nothing to give or receive. If they had listened to the still small voice crying “I am He!” then they would certainly have fared better - in my humble opinion. To an atheist I would say, if you sincerely want to know for sure if He exists or not why not act like He does and then live it and see if you are changed for the better. If it does not, what have you lost? You may even have gained a few new friends along the way.