modesty, viz. humility, honesty, simplicity, and contentment, the way we dress reflects our desire for change. That is to say, that to dress in "fancy" clothes is not dishonestly saying that we are "fancy" people. In fact, forget any notion of "fancy." Our desire is to dress with simplicity and contentment.
The basic arguments for wearing dress clothes to Mass go something like this: 1) If the Mass is the most important thing that we do all week, then we should dress according to its importance. If we were going to meet the pope, who is the vicar of Christ, would we not wear our nicest attire? All the more, we should wear our nicest attire to receive the Eucharist, who is Christ Himself. 2) We should dress in a way that does not take away from the dignity and solemnity of the Mass. Therefore, we should wear our nicest clothes. 3) We are dressing up to please God, not other people. So, we should dress in our nicest clothes.
I think we could probably come up with plenty of other examples, but they all point in the same general direction. The Mass is what it is, so wear your nicest. To that I say, "RUBBISH!" Sunday's best ought to be reserved for Sunday, but if I were to go in my closet and pull out my nicest clothes, I would be picking out my tuxedo. So, for that reason, I say, "RUBBISH!"All of the arguments above are valid arguments, but what we need to recognize is that wearing our nicest and dressing appropriately are two different things.
Dressing with humility...
Again, our desire should be to dress with humility, honesty, simplicity, and contentment. If we are going to be humble, simple, and content, we should wear attire that lacks the look-at-me-ness of the tuxedo. The tuxedo says something very different from the traditional Sunday's best suit. It says, "Look at me! What we're doing here is about us." It is totally celebratory, but it lacks the it-is-not-about-me-ness that the next step down has, viz. the suit. For example, when the president is sworn into office, he does not wear a tuxedo. Instead, he wears a suit. Afterwords, to the inaugural ball, he puts on his tuxedo. The inauguration is all about the office of the president. There is a solemn moment when he places his hand on the bible and swears his oath to uphold his office. In so doing, he commits himself to something higher than himself. At the ball, however, it is all about him. He did it. He attained his goal. It is appropriate for him to wear such clothing for such an event. If Jesus showed up to Mass, it would be completely appropriate for him to show up in a tuxedo.
Dressing with honesty...
We see something similar played out with the wedding ceremony. There is a distinct difference, an added layer if you will, about why these couples and their party wear tuxedos and the great white wedding dress. The marriage ceremony is about the couple. It is not only about the couple, but in a very special way, they are separate from the faithful at this rite while they are receiving this sacrament. In this way, the attention drawn toward them points to God.
The added layer for a couple to be married is that they dress in their baptismal garment. So, it is appropriate for the bride to dress in white. It is her sacramental gown, the same gown she was clothed in at her baptism. The same is true for a young girl receiving her First Communion. I would argue for the same to be done at confirmation, and that men should wear white too. It is more common for tuxedos to be black and we should not start changing our venerable customs on account of color preferences, but the vest and tie should be white (similar to what Pres. Obama is wearing in the picture above to the inaugural ball).
We read in Mt. 22:1-14 the parable of the wedding banquet. A king invites strangers to a weeding feast in order to fill his hall after being rejected by those he originally invited. One man at the feast is not wearing wedding clothes and is cast into the outer darkness. The story has always been understood such that the wedding garment is the sanctifying grace of God. Similarly, we put on the white garment at Baptism to signify the grace we put on in Christ.
In the book of Revelation, we read about all the faithful who have gathered around the throne of God in worship, and they have clothed themselves in white robes, robes made white by washing in the blood of the Lamb (cf. Rev 7). What we, therefore, ought to do is to put on Christ. In putting on Christ, we become sons of God, and we share in Christ's inheritance. In coming to the banquet feast of the Son, come not only as guests, but as His bride. And as His bride, we become one with Him.
As the bride, we have put on the white garment of His sanctifying grace, which we need not signify every time we come to Mass. As sons of God, we have received an office. We are coheirs because of our sonship, and out of respect for our office we should dress accordingly.
Dressing with simplicity...
Dressing with contentment...
We do not need to go out and buy a new suit or a new dress. If we have nice clothes we should wear them. If we do not have nice clothes, we should buy some. Forget Neiman Marcus and Emporio Armani. Swing by a thrift store and find something that fits and is not dingy or worn out. When you do go shopping for clothes to wear to Mass, keep in mind the principles and ask, is this humble, simple, and honest. If so, be satisfied with it. If it is already in you closet and meets our criteria, be satisfied with it.
If you want to learn how to dress with contentment, then thank God for what you have. If what you have is good, give thanks. If you do not have nice clothes and cannot afford even a $15 outfit from a thrift store, wear the nicest thing you have, and God will accept that as an earnest effort.
We ought to dress with the simplicity and humility to say, "this Mass is not about me;" the honesty to say, "I need to change," and "I have the dignity of the sons of God;" and the contentment to say, "thank you."