Over at SecretAgentMan's Dossier, I found this quote taken from Heinrich Rommen's The State in Catholic Thought

If the rights of man and the duties of authority, and the duties of man and the rights of authority, do not ultimately originate in a transcendent God who is perfect Intellect, infinite Goodness, omnipotent Will, gracious and just Providence, then there is no escape from anarchy or from tyranny. So invincible is this argument that from time immemorial philosophers have deduced a proof of the existence of God from the nature of man as a political and legal being, from the existence of the state and of the law.

I must read Rommen. Although I have never heard anything about this particular 'proof', it has always been my favorite. I have always believed that man (particularly in his social aspect) is sufficient proof of God's existence. I think that the human is only possible in the presence of God. It has always been my secret passion to develop and present this proof. I've never had the time to pursue this ambition and I am probably totally inadequate to the task so it's delightful to know that "from time immemorial philosophers have deduced a proof of the existence of God from the nature of man." I would love to study these various proofs.