A brief theology of gift...
We are said to possess that which we can freely use or enjoy as we see fit. Therefore, as Augustine says (In Joan. Tract. xxix): "What is more yours than yourself?"
A gift however, requires three things: 1) A giver, who is at the same time one who possesses that which is given and expects nothing in return; 2) that which is to be given, which is entirely and rightly possessed by the giver; and 3) a receiver, who must be open to receiving that which is freely given with no intention of returning or remunerating in some way.
To be pedantic, if I were to attempt to give a gift and the person to whom I tried to give it was unwilling to receive it, there would simply be no gift. If I were to attempt to give a gift and I expected payment for it, it would simply be a sale. If I attempted to give something that was not mine, and the person to whom I tried to give it was completely willing to receive it, the giving would be unlawful and bogus.
The only reason that would explain a thing being given in gratuity with no expectation or intention of some return is love. Here I am not speaking of some feeling or emotion, but rather, that love that impels us toward communion, namely Christian charity (caritas).
It is a love that gives of itself solely out of a desire for the good of another. It is the love that gives for another's happiness rather than one's own. It is a sacrificial love willing to give to the point of death, and it finds its source in God. St. Thomas Aquinas says, "love has the nature of a first gift, through which all free gifts are given."This first gift is God, and the Holy Spirit is His Name. St. John the Baptist tells us likewise, "A man can receive nothing unless it has been given him from heaven" (Jn 3:27).
It is most appropriate that gifts be given at Christmastime, whether we give them on Christmas Eve, Christmas Day or Epiphany; whether we give them, St. Nicholas or Santa Claus gives them, or the Christkind/Christ-child gives them. We each have our traditions of giving, and each is appropriate to expressing the miracle of God's gift of Himself out of gratuitous love to the world.
Every gift giving tradition, but in particular those which emphasize the free gift (not exchange), participate in a unique way in the mysterious way that God gives and moves us in caritas to give freely with no expectation of return.
For children, receiving a gift from the Christkind or Santa Claus on Christmas morning allows them to open their hearts to the kind of love that God has for them. St. Thérèse of Lisieux had her great conversion at Christmas. St. Thérèse committed herself to the love of Christ when she found out that that Christmas would be the last that they would receive presents. Christ's love would suffice. The relation of Christ's love to gift is incredibly tight. It is a small step between recognizing the love to recognizing Christ Himself.
For parents, giving a gift from the Christkind or Santa Claus on Christmas morning allows them to participate in that same selfless act of outpouring love that Christ performs by becoming man. St. Nicholas reminds us of this by the example of his life. St. Catherine Drexel, as well, images this gratuitous self-giving by her religious life and the exhaustion of her inheritance. Participating in the gift-giving forms in us a habit of selflessness that we ought to extend beyond our own families and into our community.
We have to remember that we cannot give but for the grace of God, and we cannot receive were He not willing to give and give through us.
We should not so easily forget our traditions. It is not better to eliminate Santa Claus and replace him with the Christkind. As long the we maintain our traditions there is no reason to reject them. So, if anyone tells you Santa Claus is heathen, you ought to answer with authority, "He is not."
G.K. Chesterton's thoughts...I would like to leave you with these thoughtful words from the man himself:
What has happened to me has been the very reverse of what appears to be the experience of most of my friends. Instead of dwindling to a point, Santa Claus has grown larger and larger in my life until he fills almost the whole of it. It happened in this way.
As a child I was faced with a phenomenon requiring explanation. I hung up at the end of my bed an empty stocking, which in the morning became a full stocking. I had done nothing to produce the things that filled it. I had not worked for them, or made them or helped to make them. I had not even been good–far from it.
And the explanation was that a certain being whom people called Santa Claus was benevolently disposed toward me. What we believed was that a certain benevolent agency did give us those toys for nothing. And, as I say, I believe it still.
I have merely extended the idea.
Then I only wondered who put the toys in the stocking; now I wonder who put the stocking by the bed, and the bed in the room, and the room in the house, and the house on the planet, and the great planet in the void.
Once I only thanked Santa Claus for a few dolls and crackers, now, I thank him for stars and street faces and wine and the great sea.
Once I thought it delightful and astonishing to find a present so big that it only went halfway into the stocking. Now I am delighted and astonished every morning to find a present so big that it takes two stockings to hold it, and then leaves a great deal outside; it is the large and preposterous present of myself, as to the origin of which I can offer no suggestion except that Santa Claus gave it to me in a fit of peculiarly fantastic goodwill.~ G.K. Chesterton, "The Other Stocking"