In the Summa Theologiae, St Thomas Aquinas works by first giving the arguments in favour of the position he rejects. He even gives arguments for saying that God does not exist before refuting these arguments. This means that when he says that something seems to be true, he actually thinks that it isn't -- but nonetheless there are reasons why people think that these positions are true.
In Question 27 of the Second Part of the Second Part of the Summa he discusses charity. For Thomas, charity is nothing to do with putting money in poor boxes or forgiving people their sins. It is the intense friendship which is identical with God's nature, which as beings made in the image of God, we share.
In the different articles of this Question, he seems to be at his most paradoxical. He insists that we should love our selves more than our neighbour. Love of our neighbour, the person near to us is based on love of ourselves. 'You shall love your neighbour as yourself'. In Article 7 he says that 'it seems that it is more meritorious to love an enemy than a friend'. I often put this as a question to study groups and, slightly suspiciously, since why would you ask this question, people say like the good Christians that they are, that of course it is more meritorious to love an enemy.
Thomas doesn't think so. He distinguishes in his dry relentless way between the lover and the beloved. In terms of who is loved, the friend is surely more loveable, more worthy of love in every way. In terms of the lover though, we might say that the love for an enemy is of greater merit because it is not done for any purpose but the love of God. (Living in the thirteenth century, Thomas had never read any newspaper editorials explaining why it is in everybody's economic and sociological self interest to live in peace and harmony.)
Thomas accepts that what we do for the love of God is of greater merit -- but then he uses an analogy: love is like a fire. The greater fire gives heat and light to a greater distance, so it is with the greater love which reaches out to enemies. Yet the fire will always warms those closer to it than those who are further away. So those who truly love their enemies, will love their friends even more.
What pervades Thomas's thought, indeed the whole mediaeval culture of Christendom, is an understanding that there is no good thing which is not, of its nature, something to be shared. I don't mean something we ought to share but something which can only exist through being shared.: there is no joy which is not of its essence something shared; truth comes to us in its being shared -- a private truth is a small truth, barely a truth at all.
We exist because God, as the supreme Good, shares truth, love and joy with all his creation, and all creation can only receive these goods as things to be shared.
Simeon and Anna understand this. Their joy was a long time coming but they knew where it was to be found. Not in solitude, not in separation, but in the temple. They never expected the Messiah to be revealed to them alone but to all the people of Israel. Anna speaks about him to all those who were expecting the redemption Israel. Mary and Joseph bring him to the temple because no child belongs wholly and completely to its parents. The child belongs first to God, then to his parents and through them to society.
As Jesus grows, he will belong to himself, but to God first. I don't say here that even Jesus has to grow, but especially Jesus. 'Jesus increased in wisdom, age and grace before God and Men' (Luke 2:52). The life of Jesus will reveal that the good things which sustain us in this life, are in fact the life of God.
God the Father loves his Son through the love of Mary and Joseph; the fire radiates through them and from them, out into the world.