These issues, which may seem baffling to Protestants who have long accepted married and women clergy, keep surfacing as controversies within Catholic communities because of a climate of confusion that has fostered, in some cases, dissent and envy (Catholic priests and seminarians who want, like their Protestant counterparts, to be married as well, and Catholic women who want, like their Protestant counterparts, to be "pastors"). Why shouldn't they?
There are a couple issues here-- one (priestly celibacy) a matter of discipline that is in principle changeable, the other (a male priesthood) a matter of doctrine that cannot. But this requires some explanation. First, matters of doctrine (like, say, the triune nature of God or divinity of Christ) quite clearly can't be revised because they conform to irreformable Catholic/Christian tradition--they're a legacy of ecumenical councils that have dogmatically codified, we believe, the teachings of the apostles and of Christ himself. Second, matters of discipline, such as whether we should kneel during the liturgy or fast on Fridays are quite clearly matters that are reformable with a view to what is pastorally prudent and helpful at a given time in history.
The question of priestly celibacy has always been understood as a matter of discipline. The Catholic Church hasn't always required that it's priests to be unmarried. Most of the original apostles, as we know, were married; as were many Catholic priests until it was judged that an unmarried priesthood could be more effective for various reasons, which I will mention momentarily. Even today, there are Catholic priests who are permitted to marry in various non-Roman rites of the Church (Byzantine, Ukrainian, Chalcedonian, Syrian, Serbian, etc.), and a number of Anglican priests who have become Catholic now continue as married Roman Catholic priests. And even in the Eastern Orthodox tradition, once a man has become a priest or a bishop, he is not permitted to marry.
Why should priests (like monks and nuns) be unmarried? Let me start with our priest, Fr. Ed Sheridan ad St. Aloysius Catholic Church in Hickory. His church doesn't look much larger than any of the other churches around Hickory. What's the membership in an average Hickory church? 200? 500? 1000? I'm not sure. But the membership of Fr. Ed's parish is over 1,400 FAMILIES. That's a LOT of people to pastor. The church seats only between 500-600, so every Sunday there are five services-- two in English, one in Spanish, one in Hmong, and another in Lahu (the Laotian language). And since not everyone can possibly attend services on Sunday alone, there are two services on Saturday-- one in English and another in Spanish. Plus there are Masses on every other day of the week, including "praise masses" Sunday nights. Imagine being pastor of a church like that and having a family too.
The first argument, then, is that a married man, as St. Paul warns in 1 Corinthians 7:25-36, will have "worldly troubles" and be "anxious about worldly affairs" and "how to please his wife." Not that marriage isn't a perfectly natural and proper calling for the man who is so called. But it may not be the most expedient calling for someone wishing to devote his or her life to "full time Christian service." My experience growing up as a missionary kid in Japan is a case in point. Many godly protestant couples have felt called to mission fields, gone abroad, and raised families there while attempting to fulfill their missionary vocations. The result has frequenly been disastrous. If you know anything about the problems missionary children often suffer growing up neglected and shuttled between countries and not knowing where "home" is, you know it's severe. When the first Christian missionaries came to Japan, long before any Protestant missionaries, in the mid-1500s, they came as celibate members of religious orders like the Franciscans and Jesuits. They were extremely successful once the native populations realized they were no threat-- since they were vowed to POVERTY, they weren't interested in extrorting wealth from the Japanese; since they were vowed to OBEDIENCE, they weren't about to undertake a political coup-d'etat; and since they were vowed to CELIBACY, they weren't interested in taking their women. Plus they had time, with no distractions. This allowed them to achieve all that they did in places like Japan, China, India, and South America--where they founded orphanages, hospitals, schools, and churches where none had ever existed before.
There are other arguments too, like the witness of the celibate priest to a higher calling amidst a world run amok indulging itself in immediate gratifications. It's surely a blessing to have physical progeny: children. But it's another to father spiritual children, and another to cultivate the charism of spiritual maternity, as St. Edith Stein writes in her treatise On Women. While marriage is a great blessing, St. Paul reminds us that those who are unmarried can devote themselves singlemindedly to the Lord without distraction; and even Jesus speaks with favor of those who have the gift of forgoing marriage in order to become, as it were, "eunuchs for the sake of the Kingdom" (I don't think He ever intended anyone to take this in a literal sense, as did Origen, the Egyptian Christian, who took two rocks to his own rocks "for the sake of the Kingdom")!
As to the other question of a male priesthood, while there are plenty of dissenting Catholics out there who keep hoping this will be changed into a matter of discipline, so that women can be admitted to the priesthood, there is simply no possibility that this will ever happen. That this has been received as a matter of inherited and irreformable doctrine from apostolic times is absolutely clear from many papal encyclicals, including Pope John Paul II's most recent statement on the letter, where he writes:
Although the teaching that priestly ordination is to be reserved to men alone has been preserved by the constant and universal Tradition of the Church and firmly taught by the Magisterium in its more recent documents, at the present time in some places it is nonetheless considered still open to debate, or the Church's judgment that women are not to be admitted to ordination is considered to have a merely disciplinary force.Now why should priestly ordination not be open to women? Surely it is not a matter of abilities or function, for there are doubtless women who can do all of the things a priest does-- preach, pray, baptize, counsel-- as good as any man. What is the reason, then? One of the best treatments of this issue, besides an essay by C.S. Lewis in GOD IN THE DOCK, is an article in CRISIS magazine (not online, fortunately) from September, 1993, by Peter Kreeft. I don't have time to summarize his points now, but he divides the issue into reasons of (1) authority, (2) sexual symbolism, (3) common good, and (4) discernment. I will quote only the first paragraph to give you a taste of the piece:
Wherefore, 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. Lk 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." (Ordinatio Sacerdotalis, May 22, 1994; for more information, click here.)
These are the simplest arguments. There are three: arguments from the authority of God, of Christ, and of the Church. (a) God invented the priesthood. The Church did not invent the priesthood. The Catholic Church claims less authority than any other Christian church in the world; that is why she is so conservative. Protestant churches feel free to change "the deposit of faith" (e.g. by denying Mary's assumption, which was believed from the beginning) or of morals (e.g. by allowing divorce, though Christ forbade it), or of worship (e.g. by denying the Real Presence and the centrality of the Eucharist, which was constant throughout the Church's first 1,500 years). . . ."Obviously this doesn't even get into the issue. But you can find plenty of other material at the link posted at the end of the earlier quotation. This has gotten far too long already.