What is love? Five theories on the greatest emotion of all

"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 nun: “Love is free yet binds us”
Love is more easily experienced than defined. As a theological virtue, by which we love God above all things and our neighbours as ourselves for his sake, it seems remote until we encounter it enfleshed, so to say, in the life of another – in acts of kindness, generosity and self-sacrifice. Love's the one thing that can never hurt anyone, although it may cost dearly. The paradox of love is that it is supremely free yet attaches us with bonds stronger than death. It cannot be bought or sold; there is nothing it cannot face; love is life's greatest blessing.

The physicist: “Love is chemistry”

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 – a mechanism we have evolved to promote long-term relationships, mutual defence and parental support of children and to promote feelings of safety and security.

The philosopher: “Love is a passionate commitment”

The answer remains elusive in part because love is not one thing. Love for parents, partners, children, country, neighbour, God and so on all have different qualities. Each has its variants – blind, one-sided, tragic, steadfast, fickle, reciprocated, misguided, unconditional. At its best, however, all love is a kind a passionate commitment that we nurture and develop, even though it usually arrives in our lives unbidden. That's why it is more than just a powerful feeling. Without the commitment, it is mere infatuation. Without the passion, it is mere dedication. Without nurturing, even the best can wither and die.