Why Do We Address God as "Father," Instead of "Mother"?

Well, because that is what Jesus did, and as Christians we don't have an independent relationship with God; we participate in Jesus' relationship.

Over the years I have heard a number of people object, "But Jesus only did that because of the patriarchal nature of ancient cultures" - the underlying assumption being that Jesus' word choice was culturally conditioned.   

The difficulty with that assumption is the freedom Jesus demonstrated throughout his ministry in breaking with the gender conventions of the time:  meeting with women privately, welcoming them to travel with him independent of their husbands, and his selection of women (unable to testify in courts of law at that point in history!) as the first witnesses to His resurrection.  His decision to name only males as apostles and address God with the masculine “Father” was not circumscribed by the outside culture.  In fact, priestesses and female deities existed throughout the Middle East as well as among the Greeks and Romans.  As the Word made flesh, Jesus’ revelation of God as Father was both free and deliberate. But why?

In Hebrew and Christian thought God is bigger than gender.  Both male and female are reflections of the Deity (Gen.1:27).  Scripture compares God to a mother (Is.49:15; Hos.11:3-4).  And yet, throughout the whole of Scripture, God is never addressed as “Mother.”  There is something about fatherhood that is more analogous than motherhood for describing God’s relationship to us.  Scripture does not come out and explain it, but I would suggest that male and female have been invested by God with an “iconic character.”  By this I mean that the differences we observe between male and female can give us insight into spiritual realities.

Think about the complementary roles the mother and father play in the conception of the child.  The father comes from the "outside," and the mother welcomes the father into herself.  The ovum produced by the mother awaits the father's sperm cell, and the union of the two produces the child’s body.  The child then grows within her mother, unable to see her father’s face until birth.   

God also plays a "Fatherly" role in every conception - coming from outside of all creation to breathe a spirit, an intellectual soul, into the child at the instant of his/her physical conception.  All of God’s actions come from “the outside” so to speak, and in this way are Fatherly.  The Church on the other hand – and the individual souls that make it up - is the  part of creation that has received God into itself and allowed him to bring forth new supernatural life.  In this analogy, whether biologically male or female, each human soul resembles the feminine.  This explains why Scripture refers to the Church as Christ’s Bride (Eph.5:22-23), and the Mother of the faithful (Rev.12:17).

As members of Christ's Body we approach God the Father through, with, and in Jesus.  In union with him we pray "Our Father, who art in heaven ..."
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This post was adapted from Through, With, and In Him: The Prayer Life of Jesus and How to Make It Our Own.

Question:  If we think about the "iconic character" attached to gender, might that yield an insight as to why the ministerial priesthood has been reserved to males?  If the priest is ordained to function "in the person of Christ" in ministering to the Lord's Bride, then doesn't the priest's masculinity function as a sacramental sign of Christ, the Divine Groom?