To ask whether women should be priests, is to ask whether Catholics should be fatherless--because, if a woman could be ordained, one would be faced either with the absurdity of calling a woman “Father,” or with the practical necessity of not regarding her as a father at all.

There is even today no clear protocol on how to address women priests in the Episcopalian church, after 35 years of the practice. Crockford’s authoritative Clerical Directory suggests “Reverend,” and “Mrs.” or “Miss” as appropriate. But notice that all fatherhood thereby vanishes, because of course it would be discriminatory to address the male in a way that one cannot address the female priests.

The most common reply one hears, when a Catholic asks why women cannot be priests, is that they never have been. So far, that is not an answer that could satisfy any reformer worth his salt.

Things are helped somewhat if one qualifies and says that, “they have never been, when they very well might have.” After all, the Church has never been culturally hidebound in the matter. Jesus appointed no women as apostles, even though he counted women among his closest followers. He shocked his followers by freely speaking with women, obviously rejecting the norms of the time. Women priests have been common in those religions the Church has existed side-by-side with.

Even so, perhaps the long consistency of the Church was the result simply of inertia, or the sheer accident that no one had posed the question? But here Catholicism is set apart from other forms of Christianity insofar as it claims to have not only a tradition but also a reliable interpreter of that tradition.

And that interpreter has given his view, repeatedly and with undeniable clarity: “This norm, based on Christ’s example, has been and is still observed because it is considered to conform to God’s plan for his Church” (Pope Paul VI) and; “in order that all doubt may be removed regarding a matter of great importance, a matter which pertains to the Church’s divine constitution itself, in virtue of my ministry of confirming the brethren (cf. Luke 22:32), I declare that the Church has no authority whatsoever to confer priestly ordination on women and that this judgment is to be definitively held by all the Church’s faithful” (Pope John Paul II).

Now when we ask “Why?”, the answer, “Because I say so,” is perfectly adequate if coming from someone with true authority over us. Obedience which requires an explanation before it will obey is not obedience but self-serving. Suppose it were St. Peter who told you, “Because I say so”; would you follow then? Suppose it were Christ Himself? It’s doubtful that someone who won’t follow the apostles which he can see (the pope and bishops), would follow those which he does not see.

The Church gives reasons as well, but our will won’t be straight and our mind clear if we aren’t resolved to follow even if we don’t understand the reasons, as in, “I believe that I may understand.”

The reasoning is deep, but its key elements are as follows.

(1) Consider first that the priesthood is a sacrament. As the old catechisms tell us, a sacrament is basically a sign that has spiritual power: it is a, “means of grace, instituted by Christ, which does what it signifies”. A sacrament has power, and conveys grace, precisely through its being a sign. If you destroy the sign, you remove the power. The sign of a sacrament is a ‘natural sign,” that is, it stands on its own and means something prior to its being used to signify grace. It isn’t a sign only because someone makes it so. The pouring of water signified cleansing even before water became the means, in baptism, of cleansing us of original sin. (Hence every sacrament reveals how nature and super-nature are in harmony.)

(2) Next consider that because a sacrament involves a natural sign, there are objective limits to the variations it can undergo without losing its power. The first baptisms were by immersion, but what about the variation that involves pouring? Yes, the sacrament has power as well if the water is poured. But suppose someone substitutes milk for water? In that case the natural signification is destroyed, and there is no sacramental power.

The Church in determining these things is not imposing a “discipline” but remarking on the objective character of the relevant signs.

(3) Finally, consider that human sexuality, too, is a natural sign. But of what? In a word, it signifies marriage (through what Pope John Paul II called the, “nuptial meaning of the body”). The division of human nature into male and female on its own signifies the possibility of marriage -- a one-flesh unity, which is procreative.

In the sacrament of the priesthood, this sign signifies the relationship between Christ and the Church, and, in signifying this, it conveys the grace that comes through that union -- especially that “higher gift than grace,” which is the Eucharist.

The maleness of the priest is essential to the sacrament, because the priest’s maleness is a sign, and that sign is essential to the power of the sacrament, as is true of any sacrament.

And that is why no one quite knows what to call a woman priest: because a woman can no more be a priest than she can be a bridegroom, husband, and father.

Michael Pakaluk is Professor of Philosophy at the Institute for the Psychological Sciences in Arlington, Va.