Anne Phillips, professor of political theory, London School of Economics

In most cases, the question that troubles people is not what is a woman, but what is a “real” woman. "Real” women are defined very differently in different periods and places.

It is one of the paradoxes of gender that we are so often told it is in our nature to be women, as if biology is indeed destiny, and yet an enormous amount of effort is put into getting us to conform to whatever is the current paradigm.

Others find the labels so incompatible with their sense of themselves that they choose to live in a different gender, undergo surgical or hormonal interventions, or redefine themselves.