There is no point in beginning something one cannot complete.
Such a project absorbs time and energy without bringing any comparable rewards. The “cost” of discipleship is the complete and permanent renunciation of personal ambitions and of worldly interests. He who is not willing to go all the way may as well not even start.
Which of you?
The twin parables of vs. 28-32 constitute a warning against lightly assuming the responsibilities of discipleship. Those guests who first accepted the invitation to the feast, only to change their minds when other interests arose, had not given the invitation serious thought when they first accepted it. The two following parables were especially applicable to such people.
A tower.
A “tower” might be either a large and costly structure (cf. ch. 13:4) or a simple one made of branches (cf. Matt. 21:33). Here, it is obviously the former. Perhaps in the town where Jesus was at the moment teaching there had been an instance of such circumstances as those set forth in the parable.