The Christian view that all intercourse outside marriage is immoral was, as we see in the… passages from St. Paul, based upon the view that all sexual intercourse, even within marriage, is regrettable. A view of this sort, which goes against biological facts, can only be regarded by sane people as a morbid aberration. The fact that it is embedded in Christian ethics has made Christianity throughout its whole history a force tending towards mental disorders and unwholesome views of life.
– Bertrand Russell