Why do we focus on churches and religious artefacts for the study of Western European design and material culture from the early $4$th century AD to approx the $15$th century AD$?$The growth of collective religious practice after The Edict of Milan in $313$ AD meant that larger numbers of people needed public meeting places.Prescribed religious ritual and ceremony needed to be housed in specially designed interior spaces that became loosely observed formulae across a great number of locations.Churches come to dominate the community's architectural activity, investment and patronage.DAll of the above