From Gen 1:27 he infers that gender is the means by which God's image is born by us.
God wanted to show the world something of his [sic] strength. Is he not a great warrior? Has he not perfromed the daring rescue of his beloved? And this is why he gave us the sculpture that is man. Men bear the image of God in the dangerous yet inviting strength. Women, too, bear the image of God, but in a much different way. Is not God a being of great mystery and beauty? Is there not something tender and alluring about the essence of the Divine? And this is why he gave us the sculpture that is woman. [p. 136]I totally agree that these aspects of masculinity and femininity find their source in God and are intertwinned in the character of God. It may be that God needed to create two genders because the richness of all those characteristics could never be expressed by a single creature.
Eldredge quotes Peter Kreeft as saying "This spiritual intercourse with God is the ecstasy hinted at in all earthly intercourse, physical or spiritual." [p. 135] Seeing sexual intercourse as a metaphor for our union with God is key to what makes sex sacred. This has made me think about a further implication: if God had to separate aspects of God's nature to express them in two genders because they could not be contained within a single gender, then the re-unification of those genders through phsyical and psychological intimacy is an even deeper indication of what God is like. The mutual knowing of each other in sex (in ideal holistic sex anyway) – the intertwining of daring and strength and beauty and allure and mystery – is even closer to the image of God than what any of us contain within our single-gendered self.
My problem with the Eldredege quote above, however, is that any attempt to classify the difference between male and female inevitably over-generalises to the detriment of both portraits. Although there are significant differences in the psychology of being male and female and consequently in the ontological categories of masculinity and femininity, defining those differences always seems to me to be unhelpfully stereotypical. Why should daring rescues not be feminine? Why can't being alluring be masculine?
And why does Eldredge continue to use pronouns that imply that the source of these rich gender differences is male? That undermines the key point he seems to be making.