“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, analyse a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.”
—Robert A. Heinlein, Time Enough for Love
This is perhaps Heinlein's most famous and most cited passage. Two things stand out for me, that the first item is “change a diaper”—all humans need to know how to look after their young—and that he includes both “take orders” and “give orders”—they are very different skills and it is the quality of a well-rounded person that he or she can do both.