Unlike a human smile, purring cannot be, as far as anyone knows, faked. — Jeffrey Moussaieff Masson

Cats are contented with their lot, with or without our approval. They have less need of us than we would like. It would flatter us to think that cats cannot survive without us, that they need us emotionally as well as materially, whereas in fact they probably do not need us in either sphere. This wounds our vanity. We need cats to need us. It unnerves us that they do not. However, if they do not need us, they nonetheless seem to love us.

The idea, to a cat, that somebody else owns him is ludicrous.

The cat does not merely experience contentment, he exudes it. You cannot be in the presence of a contented cat and not have some of that contentment rub off on you. Which surely is a good part of the reason we love cats so.