I found this one particularly fascinating.
Denis describes here how columns are a vital part of the design of the church building which is meant to be the sacramental image of the Church, the mystical body of Christ. Historically the building was so clearly identified as an image of the Church, that this is why it came to be called a 'church'.
The columns represent important people within the Church who, metaphorically, support it. Most importantly it would be the 12 apostles. Prior to the Christian era the columns represented the 12 tribes of Isreal in Jewish architecture. Even within the classical, pre-Christian tradition, columns were identified with people and different designs were ascribed to men, women and young girls. With the tradition present in both the Jewish and classical traditions that preceeded them, we can see why it made great sense, for the early Christians to incorporate the same symbolism into the design of their churches.
It is because they are symbolic images of people that there are particular aspects of design on the columns, again incorporated into the tradition, and they should not just be created as straight vertical lines that are pure structural support - as a modern architect might wish to do. It does not mean that every column should necessarily correspond precisely to the Doric, Corinthian and Ionic columns of classical architecture, but it does point to importance of columns of some form as symbolic images of people, as decoration that visibly performs a structural purpose.
The question one might have after considering this is, even if we acknowledge that properly formed columns are right for a church building, is do we need to have them in secular buildings as well? What about libraries, town halls, houses, theatres, and so on?
I would say again that the church should be the symbolic heart of the community. Therefore, just as all human activity is formed by and leads us to the worship of God, so the design of all buildings whatever their purpose should be derived from and point to what should be the focal point within the town plan, the church and so we ought to see columns in secular buildings too. All of this should be modified so that each building is appropriate to its particular purpose: a government building would have a design that is mre directly corresonding to a church, I would suggest, than a cow shed or a public convenience.