I honestly can't believe I'm going to write this.
The season of Lent is a time of fasting -- abstaining from food for a time, abstaining from meat, sacrificing some of the comforts of life to reflect on the suffering and sacrifice made by God. The beginning of Lent, Ash Wednesday, is one of the highest moments in the church calendar. It is also preceded by one of the lowest.
I've never attended a Mardi Gras celebration, but it is generally regarded as a time for general debauchery and mischief. It began as a single day -- "Fat Tuesday" is the French translation -- but in some places it is now celebrated as a multi-day celebration of venial sins, wherever they may be conveniently had. In other places, it is a much more muted occasion, but the principle remains: before you're stuck fasting and devoting yourself to holiness, live a little! Indulge your wilder side!
I consider myself a pretty straight-laced person, so the idea of 'Fat Tuesday' doesn't particularly appeal to me. However, there is a moral principle at work, that I think bears closer inspection.
God created nature, and made it good. Its current fallen estate does not and cannot override its original and intended nature: to be a vessel of God's love and care. Our Creator is good, and the Creation bears His signature. We should not fall prey to Manichean dichotomies of God fighting against an evil material universe -- the image itself testifies to its absurdity.
Moreover, we live in a place and a time with unparalleled prosperity. In contrast with every other era of history, it is nearly impossible for an individual in the modern West to die of starvation. In contrast with many other places in the world, a beggar in the modern West still carries more wealth than most of the population of the Third World. It is almost impossible to fathom the degree to which we are removed in material resources from most other peoples and places. Likewise, it's almost impossible to fathom the degree to which we fail to appreciate it.
The meaning of a sacrifice depends on the value of the thing given up. This is the foundation of all sacrifices -- from the ritual offerings at the Temple of Solomon, to the Passion of the Christ, to the modern practice of tithing. This is why Abel's sacrifice was accepted and Cain's was not. This is why Israel was command to sacrifice the firstborn of their flocks, and why no lamb with spot of blemish would be acceptable. This is why monastics and ascetics are considered holy -- not because they renounced the evil things of this world, but because they gave up the good comforts of life to help them meditate on the mercy and humility of God. This is why Catholic priests are called to a life of celibacy -- not because marriage is a bad thing, but at least partly because the voluntary sacrifice of one of life's great Joys testifies to their devotion and exclusive service to God.
If we wish to honor God with our sacrifices, we should realize the value of what we are giving up. When we fast -- when we abstain from food or any good thing either in quantity or in quality -- we should remember that we are sacrificing something that God created for our enjoyment.
If we reflect and realize that what we're giving up is in fact bad for us -- if it's an addiction, or an idol, or a sin -- then it shouldn't be the object of a "fast" but the object of a confession. We wouldn't dump the contents of our garbage bags into the collection plate if we were honestly seeking to honor God. If we did, there was probably something a bit off with our relationship with Him. The principle remains the same.
When we first surrendered our lives to God, it was in consideration of God's grace and mercy and love, borne out of the realization that He first loved us and valued us, enough to send His own only begotten Son to live among us and suffer for us and die at our hands. I believe the Calvinist doctrine of total depravity makes nonsense of God's love -- for it we were totally depraved and utterly unlovable, how could God come to value us? Rather, we are marked by His image and made in His likeness. We were made for His Presence, but fell from glory, and God stooped down to raise us back up.
The Christian case for Mardi Gras is simple. Before we fast, we should take a moment to remember just how good the things we're giving up actually are. I do not say we should indulge in such things: for good things in excess make the best idols, and gluttony is a deadly sin. But we can and we ought to find time to revel in the glory of God, revealed and imparted in His blessings and His bounty. Only then, in the full knowledge of the majesty and glory of God, and the beauty and goodness of His Creation, can we sacrifice the first-fruits of our lives with the knowledge that it is a worthy offering to the Lord.