From the Pen of John Steinbeck

"Results, not causes. The causes lie deep and simply--the causes are a hunger in a stomach, multiplied a million times; a hunger in the soul, hunger for joy and some security, multiplied a million times' muscles and mind aching to grow, to work, to create, multiplied a million times. The last clear definite function of man--muscles aching to work, minds aching to create beyond the single need--this is man. To build a wall, to build a house, a dam, and the wall and hose and dam to put something of Manself, and to Manself take back something of the wall, the house, the dam; to take hard muscles from the lifting, to take the clear lines and form from conceiving. For man, unlike any other thing organic or inorganic in the universe, grows beyond his work, walks up the stairs of his concepts, emerges ahead of his accomplishments. This you may say of man--when theories change and crash, when schools, philosophies, when narrow dark alleys of thought, national, religious, economic, grow and disintegrate, man reaches stumbles forward, painfully, mistakenly sometimes. Having stepped forward, he may slip back, but only half a step, never the full step back. This you may say and know it and know it. This you may know when he bombs plummet out of the black planes on the market place, when prisoners are stuck like pigs, when the crushed bodies drain filthily in the dust. You may know it in this way. If the step were not being taken, if the stumbling-forward ache were not alive, the bombs would not fall, the throats would not be cut. Fear the time when the bombs stop falling while the bombers live--for every bomb is proof that the spirit has not died. And fear the time when the strikes stop while the great owners live--for every little beaten strike is proof that the step is being taken. And this you can know--fear the time when Manself will not suffer and die for a concept, for this one quality is the foundation of Manself, and this one quality is man, distinctive in the universe."

--The Grapes of Wrath, Chapter 14.
He's my favorite author, and this is my favorite chapter in my favorite book. Everyone should read the book, and if not, read the entire chapter 14.