Good questions all...................

 In your favour of April 8th, You “wonder for what good End the Sensations of Grief could be intended”? You “wish the Pathologists would tell Us, what the Use of Grief, in Our Œconomy, and of what good it is the Cause proximate or remote.” When I approach Such questions as this, I consider myself, like one of those little Eels in Vinaigre, or one of those Animalcules in black or red Peper or in the Horse radish Root, that bite our Tongues So cruelly, reasoning upon the το παν ["totality"].  Of what Use is this Sting upon the Tongue? Why might We not have the Benefit of these Stimulants, without the Sting? Why might We not have the fragrance and Beauty of the Rose without the Thorn?

-John Adams, from a letter to Thomas Jefferson, May 6, 1816