Verified by Psychology Today. The Mysteries of Love. If love can be meaningfully said to be rational and irrational, as I have argued in my latest book On Romantic Love: Simple Truths about a Complex Emotion , one cannot help but wonder what to say about sex. In my opinion, there is little doubt that sex can be unjustified in almost exactly the same circumstances as love. If having sex with someone is likely to subtract from your wellbeing, then the activity is unjustified or irrational. But when sex is unlikely to subtract from your wellbeing, it is perfectly permissible as long as the encounter is consensual.