From a letter to his father, quoted in George MacDonald and His Wife by Greville MacDonald
1) I have a great craving for definite theories, for understanding the universe (including God). So I understand the struggle between understanding and doing; both are necessary, but doing is something that's necessary even when understanding is elusive. That's what love is about.
2) This could also be a definition of faith. Not to the exclusion of reason, I don't think (MacDonald was hardly a thoughtless man himself!), but in the sense that faith requires occasionally walking blind. I'm not good at this, yet, or at least I don't think so, but with God's grace I am growing in it.