how do you think the division of the Christian church into clergy and laity helped them spread their beliefs?

Answer 1

I suspect this method did lead to a quicker expansion of the Church, if only because of the relative numbers of each. The clergy were, by necessity, limited in numbers. Clergy had to be educated, at least to some degree, which took both time and money. Clergy tended to be of somewhat-upper class, since the general populace didn't have luxury of foregoing hours working in the fields, etc., to learn to read and study scripture. If, when you speak of "laity", you mean such things as "lay brothers", the premise is still accurate. Some religious orders allowed lay brothers--non-ordained monks, essentially, who never went through the whole process of ordination--to serve the community without having gone through the lengthy course of study that those entering the priesthood did.

That aspect, though, also illustrates the utility of that model. Priests were considered "apart"--they were holy, not really part of the community, and in some cases a little frightening since they had the direct ear of God. Lay brothers, or other lay people who were closely aligned with the Church, were nonetheless familiar figures in their towns or villages. They could minister to their neighbors while still remaining approachable. And, because there were many more such people available than priests, they could spread the religious word much more widely. Some villages would be too small for their own priest, but would usually have some form of godly lay person who could fill that role in everything other than administering sacraments.