"One is not born, but rather becomes, a woman." This quote, by philosopher Simone de BeauvoirA French feminist philosopher best known for her book The Second Sex., is often understood as the founding statement of modern feminism.

The argument that differences between men and women are caused by social factors, not biology, has driven the women's movement for decades. Using this principle, feministsPeople who call for women's rights with the aim of achieving gender equality. There are different ideas within the feminist movement. insisted that women must have all the same rights and opportunities as men.

Now some thinkers are claiming that we have got it all wrong. They call themselves "reactionary feminists", and they claim differences between men and women cannot be abolished.

Men, they say, are biologically destined to be more aggressive and less emotionally attached, while women have an innatePresent naturally. inclination to be more conciliatoryLikely to want to end a disagreement. and protective. Denying their instincts has made them unhappy, not free.

True feminism, they argue, should stress women's "separate but equal" role alongside men, and trumpet the advantages of marriage as an outlet for women's caring instincts.

But critics say this is just bad science. It means drawing a line between "natural" and "social" that does not really exist.

There is no way of proving that human beings have "natural" psychological differences that are independent of society, they argue, because there are no human beings that do not live in societies. Forming societies could be understood as part of our nature.

So it is silly, they argue, to describe some influences as "social" and others as "biological": societies are themselves biological.

And, they claim, even if some instincts could be shown to be "natural", this would not make them either better or more fundamental than "social" instincts.¹

Some worry the arguments of the reactionary feminists also cleave very closely to those made by right-wing anti-feminists.

This group also argues that people's behaviours are determined by evolutionary psychologyThe study of the ways in which the mind was shaped by pressures to survive and reproduce.. Women, they say, are hard-wired to be meeker than men, which means they will never be as career-orientated as men. As such, there is no point in aiming for things like equal pay.

Sceptics argue the "reactionary feminists" are giving them everything they want.

Yes: We cannot pretend that biology does not exist. Men and women will both be happier if they are allowed to fulfil their natural instincts.

No: People's lives are not determined by biology. Men and women have been socialised to be the way they are, and to be truly free they need to be liberated from these social pressures.

Or... The rise of this opposition between the social and the biological should concern us all. It fuels a movement that wants to control how people express themselves and set their paths for them.