Quotes from Eugene Kamenka

All moral relationships are indissoluble according to their concept, as one can easily convince one's self by postulating their truth. A true state, a true marriage, a true friendship, and indissoluble. But no state, no marriage, no friendship corresponds completely to its concept... (Karl Marx)

A person who contracts a marriage no more makes or invents marriage than a swimmer invents nature and the laws of water and of gravity. Marriage, therefore, cannot adapt itself to his caprice, to his arbitrary will, but his caprice, his arbitrary will, must adapt itself to marriage. (Karl Marx)