How does a parent or teacher explain to a young person why the Church is against sex outside marriage – or rather, why the Church is in
favour of sex exclusively
inside marriage (and marriage between a man and a woman, to boot)? I don't know, but one important argument that is often left out concerns the nature of the human person, which is quite different from what is customarily supposed.
If human beings were simply living bodies ("ensouled bodies", because a soul is an animating form) like other animals, there would be no very strong reason against promiscuity. Evolutionary and social reasons would not suffice. Psychological factors might well be against it. Not everyone is inclined, like
