I believe the answer is "A heavenly Muse" (since he's asking for help to serve God)
Imagination, without any knowledge of the impossible you test the boundaries and redefine it. Logic is linear and does not question beyond already known concepts, although it may aid in current, defined situations- imagination is able to aid in all!
Answer:
The primary functions of the spleen are to filter blood and to serve as part of the immune system.