The grace of God means something like: Here is your life. You might never have been, but you are because the party wouldn't have been complete without you.
Compassion is sometimes the fatal capacity for feeling what it is like to live inside somebody else's skin. It is the knowledge that there can never really be any peace and joy for me until there is peace and joy finally for you too.
It is as impossible for man to demonstrate the existence of God as it would be for even Sherlock Holmes to demonstrate the existence of Arthur Conan Doyle.