Part I: Why do Catholics call the Mass a "sacrifice"? Who is being sacrificed? If it's Christ doesn't the Bible say that Jesus was offered "once for all"?

“Love the Lord with all your heart, and with all your soul,

and with all your MIND”--Matt 22:37

Question:  Why do Catholics call the Mass a "sacrifice"?  Who is being sacrificed?  If it's Christ doesn't the Bible say that Jesus was offered "once for all"?

Ah, the Mass!  No other Catholic practice is more misunderstood and maligned than the Holy Sacrifice of the Mass (and this rejection is often by Catholics who really have no clue about this "powerful supernatural drama that enfolds them"--from Scott Hahn in The Lamb's Supper). Not only is it rejected and scorned-it's borrrrring!  it's repetitive!  the priest gives a monotone homily I've heard a million times!  the music and the singing are horrible!!--but it seemingly can't compete with the lively, spirit-filled Evangelical Christian services which are attracting our poorly-catechized fellow Catholics in droves.  (Again, Time Magazine reports that Catholics are the largest religious group in the US, and that ex-Catholics are almost the second largest religious group!)Apologist Tim Staples, a convert from the Assemblies of God, studied his way into the Catholic Church.  He knew Catholicism was true before he ever set foot inside a Catholic Church.  But the first thought he had when he went to investigate his first Mass was, "Why does everyone look so mad?"   <sigh...>  This is indeed a sad testament to the poor catechesis we've had.  We know not the magnificent treasures we have in the Church. 

I must say that I have attended a few non-Catholic worship services, and as far as making me feel welcome and wanted, and seeing people in love with the Lord, these services put Catholics to shame.  I remember thinking, "Wow!  Everyone really wants to be here.  And they seem to want me to be here, too!"  The Catholic Mass cannot compete with these other services with their lively, entertaining, articulate, energetic, charismatic pastors preaching a message that's palatable and funny and insightful.  While driving recently I passed a mega-church that had a 3 story blow-up slide, easily visible from the highway.  That's attractive to families.  That makes people want to go and check it out.

Sadly, we don't have that.

But, we have something better.

Or, rather, Someone better.

We have Jesus.  Present, Body, Blood, Soul and Divinity.  It's where we become One Flesh with Him. The Mass is where the life-giving Presence of Jesus in the Bessed Sacrament is given to us.  The Mass is where we "consummate our marriage" to our Beloved.

(Note: I am not saying that Jesus is not present in these other non-Catholic worship services.  For of course where two or three are gathered in His name, He is there!   But He is not there in the Eucharist.  No one can enjoy the One Flesh Union--this profound, sublime intimate joining of man with his Beloved--unless the Eucharist is there.)

At each and every Mass we have heaven crashing to earth.  Author Annie Dillard writes that if Catholics really understood what was happening at the Mass we'd all be wearing crash helmets and not dainty little Sunday hats to Mass!  We have the Church Triumphant (the angels and saints) present with us at each and every Mass worshiping with us before the Eternal Throne of God.  It ought not matter one whit that the priest mumbled the prayers, the cantor sang off-key or that we've heard the same parable for the 50th time.  The mystery of the sublime reality of the Mass surpasses and overwhelms even the worst homily/singing/priest/readings/ etc etc etc.
From Fr. Benedict Groeschel's introduction to Scott Hahn's The Lamb's Supper:

"I always feel a twinge of annoyance when I see in a college or a hotel a list of "religious services" and observe the Mass listed at 9 A.M. The Mass is not a religious service. When Catholics say morning prayer or the recitation of the rosary or even have Benediction of the Blessed Sacrament, that's a service. It's something that we do for God, similar to the public prayer of any religious denomination. But the Holy Sacrifice of the Eucharist, the Divine Liturgy, is not precisely - in its essence - done by man at all.

Let me tell you, I've been a priest for forty years and I never conducted a "'service" called a Mass, I was a "stand-in" for the High Priest, to use the words of Church teaching, I was there functioning in persona Christi - in the person of Christ, the High Priest of the Epistle to the Hebrews. People do not come to Mass to receive my body and blood, and I could not have given it to them if they did. They come for communion with Christ."

"Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect" - 1 Peter 3:15