Guardian: “What is love” was the most searched phrase on Google in 2012, according to the company. In an attempt to get to the bottom of the question once and for all, the Guardian has gathered writers from the fields of science, psychotherapy, literature, religion and philosophy to give their definition of the much-pondered word.

The physicist: ‘Love is chemistry’

Jim Al-Khalili

Biologically, love is a powerful neurological condition like hunger or thirst, only more permanent. We talk about love being blind or unconditional, in the sense that we have no control over it. But then, that is not so surprising since love is basically chemistry. While lust is a temporary passionate sexual desire involving the increased release of chemicals such as testosterone and oestrogen, in true love, or attachment and bonding, the brain can release a whole set of chemicals: pheromones, dopamine, norepinephrine, serotonin, oxytocin and vasopressin. However, from an evolutionary perspective, love can be viewed as a survival tool –