'Women," a Chinese proverb advises, "hold up half the sky." But which half? What seems like an academic riddle is actually part of the political debate in Tunisia, where a proposed change to the draft constitution has provoked heated debate and demonstrations by thousands of people last week.
The crux of the argument is whether women are "equal", or "complementary" to men. The distinction may seem minor, but it has profound repercussions.
Demonstrations were called after Ennahda, the Islamist party that dominates Tunisia's Constitutional Assembly, which is rewriting the constitution, proposed inserting a new clause.
The wording was clear: the roles of men and women "should complement each other within the household". It was that word - complement - that caused the problem. Thousands of Tunisians took to the streets to demand that it be excised and the original wording referring to equality restored to the constitution, which is among the most progressive in the Arab world regarding gender equality.
Complementarity is at the heart of how Ennahda sees the role of women: party members believe that women have an equal, but different, role to play in the society. This is not an uncommon view among religious groups, especially from the Abrahamic faiths, who believe God created mankind in pairs and assigned different roles to each gender.
In common with other Islamists, Ennahda has what might be called an "Islamising" project. These groups believe that reordering society based on religious principles will solve many of the social challenges of modern life.
In particular, Ennahda looks to the family unit as a guarantor of social stability - a safeguard against the "instability" created by single mothers or extramarital sex. That means that Islamists have a necessarily conservative view of gender relations - one that puts them at odds with many others in Tunisian society. Urban Tunisian women expect access to education, professional opportunity and the freedom to define their own relationships with men. Those who do not subscribe to the Islamist worldview find themselves at odds with Ennahda's ideas.
In itself, that isn't an insurmountable position. Islamists may form the majority in the Constitutional Assembly, but they do not control it - they share power with two other large parties, the Congress for the Republic and Ettakatol, which are both broadly secular.
For the most part, Ennahda appears to have sought a moderate way forward. Indeed, the head of the party, Rachid Ghannouchi, has stated clearly that he wants the final constitution to represent all Tunisians. The party issued a statement earlier this year repudiating a fear among secular Tunisians that it would insert a clause about Sharia law into Article 1 of the Constitution.
That makes this proposed insertion of women's "complementary" role something of a political misfire. Ennahda is picking an unnecessary fight.
The party tried to row back a bit from the wording, arguing that "complementarity should be construed in a positive way", according to Farida Abidi, an assembly member. She pointed out that there is a clear article in the proposed constitution: "All citizens have equal rights and duties before the law notwithstanding any kind of discrimination whatsoever."
But this is slightly disingenuous. What critics of complementarity are arguing for is the freedom to choose roles in society. Equal treatment before the law is not the same as equal participation in society.
The Ennahda - and Islamist - idea of gender equality is to delineate a particular sphere of action for women and to protect their participation in that sphere. But that isn't the same as saying that women can participate freely in all aspects of society and - especially - choose which aspects and which roles they want.
Ennahda does itself no favours by trying to conflate these two differing ideas of equality. By doing so, the party fits a caricature of duplicitous politics described by its opponents.
The problem with "complementarity" is that it limits women's options. Perhaps, arguably, it enshrines and even protects them within a certain sphere - but it limits women to that particular role.
Complementarity comes down to a particular conception of gender freedom. Ennahda wants to construe it positively, marking out a sphere of action and offering it to women. It sounds like the party is protecting women's rights, but it is in fact removing the right to choose.
The clause is out of step with Tunisian society - but it is also a political misstep. The real challenge for the party is not the divided secular-liberals, but the strident Salafist wing of the Islamist movement.
By pushing this interpretation, Ennahda is simultaneously ceding political turf to its real challengers, while also alienating potential allies among the secular-liberals. Ennahda cannot compete with the Salafists on hardline ideas of women's roles - they will always lose. Better to position themselves as a centrist party, mediating between the divided secular-liberals and the hardline Salafists.
The rise of Islamists after the Arab spring has brought new political ideas about gender equality, ideas which clearly resonate with many people in the Middle East. It is right that Islamists promote their ideas - but not at the expense of existing norms, nor by staging turf wars over women's rights.
On Twitter: @FaisalAlYafai