COMPLEMENTARITY (NATURAL PAIRING):
Arguments for other-sex marriage on the basis of the natural pairing of men and women rest on an affirmation of their essential complementarity. The theological problem with this is one of anthropology, as it rests upon an affirmation of essential difference between men and women. Such essential difference is necessarily sexist because it asserts that the difference between men and women goes “all the way down.” Insofar as this difference is essential no thorough claim on equality can be made because any designation of commonality (“humanity”) is just as basic or fundamental as the designation of difference (male or female). And it seems rather clear to me that the UMC explicitly affirms the essential commonality or sameness of men and women that precedes any differences.
While there is no official statement or affirmation on the topic of theological anthropology in the UMC (as we don’t have an official systematic theology), a broad but foundational thread is implied by The United Methodist Church’s two most important denominational texts, the Book of Discipline and the Book of Worship. Their overlap on the issue is in very clear statements about the essential equality of men and women, an occurrence which should not be easily dismissed. This means that a complementarian perspective based on the essential difference between men and women is at odds with the denomination’s strongly implied and consistently stated position on the issue.
Among its social principles, its only direct statement on anthropology, the Book of Discipline states,
We affirm with Scripture the common humanity of male and female, both having equal worth in the eyes of God. We reject the erroneous notion that one gender is superior to another, that one gender must strive against another, and that members of one gender may receive love, power, and esteem only at the expense of another. We especially reject the idea that God made individuals as incomplete fragments, made whole only in union with another. We call upon women and men alike to share power and control, to learn to give freely and to receive freely, to be complete and to respect the wholeness of others. We seek for every individual opportunities and freedom to love and be loved, to seek and receive justice, and to practice ethical self-determination. We understand our gender diversity to be a gift from God, intended to add to the rich variety of human experience and perspective; and we guard against attitudes and traditions that would use this good gift to leave members of one sex more vulnerable in relationships than members of another. 
This language of “common humanity” is surely a reference to the language of “humankind” in the first chapter in Genesis where the writer explains that, “God created humankind in his image, in the image of God he created them; male and female he created them.”  Such a sentiment is strongly supported by Paul in his letter to the Galatians when he states, “There is no longer Jew or Greek, there is no longer slave or free, there is no longer male and female; for all of you are one in Christ Jesus.” 
The critical overlap here is found in The United Methodist Book of Worship concerning the services for Christian marriage. Here the Book of Worship is very clear and careful to neither ask nor establish any different vow, service, or commitment of the husband and the wife.  The language for the husband and the wife is identical and this point cannot be missed. The Book of Worship indicates no essential difference between men and women liturgically, here or elsewhere. In the ceremony for marriage the Book of Worship’s theological implication is that women and men are essentially equal. While I do not wish to overstate this point, it is stronger than mere implication alone because of its liturgical location. It is here, in the exchange of vows, that traditional gender roles have been historically located. Their replacement with lines of equality is not without significance.
While some (i.e. biological and chemical) differences surely exist between women and men both the Book of Discipline and the Book of Worship clearly indicate they are in no way determinate for worth, value, status, capacity, or role. Insofar as a theological anthropology can be discerned from the commitments of The United Methodist Church as expressed in these two core documents, it would include the essential equality between men and women.
In the next part (part IV) I explain why the UMC should move toward full inclusion.
 The Book of Discipline of the United Methodist Church, 2012, ¶161E (110).
 Genesis 1:27 NRSV.
 Galatians 3:28 NRSV.
 The United Methodist Book of Worship (Nashville, TN: The United Methodist Publishing House, 1992) 115-138.