It is cruel and insensitive to interpret an affair as a symptom of sickness in the relationship, as it leaves the 'cheated-on' partner - who may already be feeling insecure - to wonder what is wrong with him Many people have sex outside their primary relationships for reasons that have nothing to do with any inadequacy in their partner or in the relationship.

The Ethical Slut: A Guide to Infinite Sexual Possibilities (ed. 1997)