The idea that men and women have been designed by a supreme power as complements to each other is common both in Christianity and in Islam. Most recently I spotted a reference to it in an article about the Catholic Church and its woman problem:
Helen Alvare, a law professor at George Mason University and a consultant at the Vatican's laity office, said the language in the draft paper was remarkable given that it calls for "collaboration and integration" with men within the church. She said that mirrors findings from leading business consultancies that companies do better when men and women collaborate at every level.
"That statement is the strongest endorsement I have seen in a church document for what we sometimes call complementarity within the church," she said in a phone interview.
Bolds are mine.
I obviously clap my hands very hard for any positive change for women within Christianity, Judaism and Islam. But I'm not a friend of the complementarity concept, not at all.
First, women and men are a lot more similar than they are different, and I believe that both genders need many of the same things. To stipulate something different is almost like asking people to live on either just bread or on just water. Parts of you will die if your diet is that monotonous.
Second, there are soul-killing aspects in the rigid assumption of separate spheres by gender, and in extreme cases this leads to women losing their right to go out and watch the sunset or to get a job (assuming that the public sphere belongs to men). One soul-killing aspect to consider is the fact that the complementarity is almost never defined by women but a few powerful male clerics.
Third, the complementarity assumption does great violence to those individuals (and I guess they are many) who suffer under the gender roles they have been assigned. And when complementarity holds hands with the assumption of women's inferiority, many of those sufferers will be women.
Finally, it's very important to remember that complementarity in roles, rights and obligations doesn't have to look like a cake divided into two equal halves, one given to men and one given to women.
It could also be a cake divided into one tiny sliver and the huge remainder, and the sliver is given to the women. Note that this division is also complementary, because the two parts add up to the whole cake! Or the good and tasty bits of the cake could be given to one gender while the other gets the moldy corners.
If none of that convinced you just consider how I would arrange the world if all other people would have to be complements to me. Wouldn't the risk be pretty high that I'd pick all the plum roles, all the roles with prestige and freedom, and that I'd leave the rotten bits to you lot?