"Love is the expansion of two natures in such fashion that each include the other, each is enriched by the other. Love is an echo in the feelings of a unity subsisting between two persons which is founded both on likeness and on complementary differences. Without the likeness there would be no attraction; without the challenge of the complementary differences there could not be the closer interweaving and the inextinguishable mutual interest which is the characteristic of all deeper relationships."