In yesterday’s reading from Philemon I was struck by S. Paul’s peaceful and joyful tone. An old man alone in prison, it seems that Onesimus has been sent to him as a consolation. He says that Onesimus has become a son to him, and is as dear to him as his own heart, “whom I would have retained with me.” But he sends him away quite joyfully. In his place I would have found plenty of excuses to keep him with me. After all, I am in prison, I need Onesimus far more than Philemon. Moreover, it is hardly fitting that Philemon, a Christian, should keep another Christian as a slave; he ought not to return. I think it is often the case that while fooling myself into thinking that I am giving everything to God, I am in fact finding excuses to retain some little consolation for myself. (“Lord, I give everything to you, I shall even forgive so-and-so, but not till tomorrow, today I need to savor my anger… This little consolation I must have..”)
Perhaps we do not have the same tranquil joy in the faith that Paul has, because we are always trying to retain something for ourselves. I think this is the key to yesterdays Gospel: “If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea and his own life also, he cannot be my disciple.” We must “hate” everything in which 
we are tempted to seek our consolation apart from the Lord. The two parables that our Lord gives in explanation have puzzled me for a long time. Preaching on them yesterday, I departed from the consensus of the Fathers in my interpretation. The Fathers all interpret the tower as Christian perfection. Thus Cornelius a Lapide, after summarizing the Fathers concludes that it is better not to become Christian at all if one is not willing to give up everything. Although I was taken in by this initially, I now think that this cannot possibly be right. For if it was no-one could become a Christian. Who looking at his resources can really says that he has enough to build that tower? And we don’t have a choice; we are commanded to become Christian. (As Notburga points out.)
S. Thomas gives a somewhat more subtle interpretation than a Lapide in the very last article of the IIa IIae. It is the magnificent article in which he argues that one ought not to deliberate long before entering the religious life. Objection 3 brings up the tower parable, taking the tower to refer to religious life. S. Thomas does not disagree that the tower refers to the religious life, but he gives a different interpretation of what calculating means:
Again it need not be a matter of deliberation whether one ought to renounce all that one has, or whether by so doing one may be able to attain to perfection; whereas it is a matter of deliberation whether that which one is doing amounts to the renunciation of all that he has, since unless he does renounce (which is to have the wherewithal) he cannot, as the text goes on to state, be Christ’s disciple, and this is to build the tower.
But I am still not convinced. It seems like the whole point of the parable is “don’t even try,” don’t build the tower. And the next parable seems to reinforce this, “don’t fight the war.” Therefore I propose a different interpretation of the tower. The tower is the attempt to retain something as our own. Towers were, in fact, often used as look-out points to watch over one’s possessions. It seems to me that our Lord is saying, “don’t even try; you don’t have the resources to keep something for yourself.” Whenever we try to hold on to something as our own, and to find our consolation in that rather than in God, then God becomes suddenly our enemy, threatening our stuff; we seem like a king with ten thousand facing twenty thousand. So our Lord says “don’t even try; give up all your possessions.” “Every one of you that doth not renounce all that he possesseth, cannot be my disciple.” (I would be interested to see what Berenike thinks of this attempt at an answer to her question).
So I think S. Paul’s tranquility is the result of having really given up everything, and experienced that everything which we give up we receive again transformed. And this is what he tries to teach Philemon:
For perhaps he therefore departed for a season from thee, that thou mightest receive him again for ever: Not now as a slave, but instead of a slave, a most dear brother
Everything which we give up we recieve again a hundred fold; not as a slave (ordered to us) but as a brother (ordered together with us to God).
