The heart is just like a fertile soil or a barren desert: it shows love or lack of love, the productive faculty or destructiveness. There are different kinds of stones; there are precious stones and there are pebbles and rocks, and so among human hearts there is a still greater variety. Think of those whose thoughts, whose feelings have proved to be more precious than anything the world can offer: the poets, the artists, the inventors, the thinkers, the philosophers, and then the servants of humanity, the inspirers of man, the benefactors of mankind. No wealth, no precious stone, whether diamond or ruby, can be compared with these, and yet it is the same quality. Then there are rock-like hearts: one may knock against them and break oneself, yet they will not move. There is a wax-like quality in the heart and there is the quality of the stone; there are melting hearts, and hearts which will never melt.