"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects."
It's a very stirring quote, and one I used to like. But the only way to do novel work is to go far enough in one direction that you get past the problem space all the specialists have already covered, and that seems hard to do part-time.
-Robert A. Heinlein