Eternity.

In my view the man who wrote most wisely about what good architecture means to culture was Sir Christopher Wren.  Few people know that Wren wrote anything about architecture; but this is what he said, in his Parentalia:

Architecture has its political use.  Public buildings being the ornament of a country, establishes a nation, draws people and commerce; makes people love their native country, which passion is the original of all great actions in a Commonwealth.

The emulation of the cities of Greece was the true cause of their greatness.  The obstinate valour of the Jews, occasioned by the love of their Temple, was a cement that held together that people for many ages and through infinite changes.

Architecture aims at eternity; and therefore the only thing incapable of modes and fashions in its principles is the Orders.

Quinlan Terry continues ...