The complementarity of the sexes is a minefield. On its face it is a doctrine of "different but equal" -- men and women are different, yet they are equal -- which might look suspiciously like other notions, such as "separate but equal," which we reject. If the sexes are equal, why not simply say they are equal, and leave it at that?

Again, it is difficult to make any general claim about the sexes which does not admit of exceptions. A claim about how nature tends to express itself, if it is true at all, will be true only "for the most part": for example, "men tend to be (for the most part are) physically stronger than woman." No doubt the average strength of men is greater than the average strength of women, and the strongest man will be stronger than the strongest woman. But any particular woman might be stronger than a particular man, or even most men. To apply the generalization to that particular case seems an unfair "stereotyping." Shouldn't one decide particular cases on its merits? But then the generalizations have no useful role.

Again, it can seem to us now that much behavior in the past, which was thought to belong to men or women by nature, was solely the result of conventional practices. We are wary of acting out of our subjective "biases," especially if they mask selfishness. So the safest course would seem to involve not trying to turn our own biases into universal truths.

Given this minefield, one would hope that the Church, in what it says about this topic would show some dexterity of foot. The Catechism does so, I think, showing tremendous refinement in what it says, in how it says it, and in what it leaves unsaid. The Church says enough to guide while leaving ample room for freedom.

Consider "different but equal." If the notion were hauled out simply to apply to sexual difference, one might be concerned. But it is presented as rooted in the most fundamental doctrine of Christianity, the Trinity: "God is love and in himself he lives a mystery of personal loving communion. Creating the human race in his own image..., God inscribed in the humanity of man and woman the vocation, and thus the capacity and responsibility, of love and communion." That is: the notion of "different but equal" applies to God as a communion of persons. It seems correct and ennobling to say that man and woman together image God, right? But then you can't have it both ways. You cannot assert this appealing and ennobling notion, which clearly enhances the dignity of both man and woman, yet deny complementarity.

Even the word the Church chooses for sexual difference, "complementarity," implies equality. Complementarity is mutual harmony and fit. Only things which are equal can fit "with each other." Two pieces of a puzzle fit with each other and are equally pieces, but consider in contrast a picture and its frame: these are unequal, and, just so, although we say that "the frame complements the picture," it would be absurd to say "the picture complements the frame."

The next thing the Catechism does, is to delimit the doctrine's scope. Here again it teaches in a non-arbitrary way, drawing on fundamental principles richly and variously supported elsewhere. Just as a human being is not a mind or a spirt, it says, so any fundamental bodily difference, such as that between male and female members of the species, must ramify throughout all of human nature: "Sexuality affects all aspects of the human person in the unity of his body and soul."

However, although sexual complementarity affects all that a person is, it does not equally affect everything that a person does, which makes sense, since complementarity is after all a kind of reciprocity. The Catechism teaches: "It especially concerns affectivity, the capacity to love and to procreate, and in a more general way the aptitude for forming bonds of communion with others." That is to say: look for sexual complementarity to be important within the household, and outside the household, insofar as affection and bonds of communion come into play. One would not, for example, expect to see a male and female surgeon perform differently, yet each might make a different kind of contribution to the comradery of the operating team, or have different kinds of personal obstacles to overcome, beside relating to family members in distinctive ways.

But what precisely are those distinctive ways? To explain and clarify, the Catechism might have pointed to the mountains of scientific results about sexual differences, but it does not. Tellingly, it does not even use the traditional language that the father is the "head" of the household.

Rather, the Catechism's treatment concludes with a general directive. It states that everyone is bound to consider how his or her own sexual complementarity advances the goods of marriage, the flourishing of family life, and more broadly the tone of civic friendship in society (2333). That is, it gives a recipe for creative discovery: work out by your best lights, and together with your husband or wife, if you are married, how this complementarity will be observed, to advance the mentioned goods.

In the end, the Catechism leaves us, appropriately, with freedom -- not to do what we want, but to identify and follow what sexual complementarity implies in our own circumstances.

Michael Pakaluk (A.B., Harvard; M.Litt., Edinburgh; Ph.D., Harvard) is Chairman and Professor of Philosophy at Ave Maria University.



- Michael Pakaluk is Professor of Ethics and Social Philosophy in the Busch School of Business at The Catholic University of America. His book on the gospel of Mark, ‘‘The Memoirs of St. Peter,’’ is available from Regnery Gateway.