Firmitatis, Utilitatis, Venustatis
In my opinion, stability and safety is the most important principle of architecture. Otherwise, architecture could collapse or even harm people. Utility is secondly important, because people usually build architecure for some specific purposes to improve human life, like memorial or living. I think beauty is the least important. Only if we meet the first two principles, will beauty have meanings. Otherwise, beauty cannot last long and cannot be fully appreciated by human.