Asked why he so rarely wrote about love, the late, great Kurt Vonnegut quipped that if you put love into a novel, it just takes over. There's no room for anything else. So he stayed away. As in fiction, so in life. Enter love, and little else matters. Habitual concerns and ways of thinking about the world vanish. Meaning resides only in the other. You're in a state of rapture, mixed with longing and pain. Bye-bye, reason and affairs of state.
From the outside, falling in love can look very like a falling into madness. Obsessiveness, delusion, psychotic identification, paranoia, magical thinking and manic highs and lows rule the lover's day. As Shakespeare noted long ago, "The lunatic, the lover and the poet / Are of imagination all compact". They share "seething brains" and "shaping fantasies, that apprehend / More than cool reason ever comprehends". Love ranked high in the precipitating causes of madness listed by William Black, who ran Bedlam in the early 19th century. Freud's patients, too, fell ill of love and its stalking partners sex and hate, though, ever a dab hand at the logic of opposites, Freud also talked of a cure through love.
When I had finished working on Mad, Bad and Sad, my history of women and the mind-doctors, I found myself wanting to explore love – one of our last socially sanctioned forms of madness. Love doesn't (yet) figure in the Diagnostic and Statistical Manual of Mental Disorders, that ever-expanding psychiatric bible which has colonised so much of our behaviour over the past 60 years, in the process turning our inner lives into fodder for tick-lists and shrinking the confines of the normal.
So I set out on the journey that led to All About Love – an anatomy of that unruly emotion, past and present. I had worries about finding the right language, one that was neither sentimental or sententious goo, nor psycho-babble. I had a great many questions, too. What are the constituent parts of passion, common to so many cultures and for so long that it seems all but universal? Who do we fall for and why, and, indeed, when? Why do we commit adultery and so readily triangulate our twosomes, whatever our aspirations, wishes and vows? Why do some of us "fall" over and over again, only sometimes breaking out of a pervasive pattern? How might love be different for men and for women? How has the nature of intimacy changed over the centuries? What is the impact of our hyper-sexualised culture and our rampant social networks on our ways of loving? Can love be sustained and how? Is marriage love's apogee or its end?
• This article was amended on 14 February to correct the spelling of the column's title.
