A theory is the more impressive the greater is the simplicity of its premises, the more different are the kinds of things it relates and the more extended the range of its applicability.
If one's life is simple, contentment has to come. Simplicity is extremely important for happiness. Having few desires, feeling satisfied with what you have, is very vital: satisfaction with just enough food, clothing, and shelter to protect yourself from the elements.
As an explanation of the world materialism has a sort of insane simplicity. It has the quality of a madman's arguments; we have at once the sense of it covering everything and the sense of it leaving everything out.