Reinhold

 From theologian Reinhold Niebuhr (source):

Nothing that is worth doing can be achieved in our lifetime. Therefore, we must be saved by hope.

Nothing which is true or beautiful or good, makes complete sense in any immediate context of history. Therefore, we must be saved by faith.
Nothing we do, however virtuous, can be accomplished alone. Therefore, we must be saved by love.
No virtuous act is quite as virtuous from the standpoint of our friend or foe, as it is from our standpoint. Therefore, we must be saved by the final form of love, which is forgiveness. 

Even if you aren't familiar with the name, you've almost certainly seen his most famous quote (source): 

God, give us grace to accept with serenity
the things that cannot be changed,
courage to change the things
which should be changed,
and the wisdom to distinguish
the one from the other.