The Establishment Clause fosters religion :: Posner

Extract:

Although atheists are in the forefront of litigation against alleged establishments of religion, there is a powerful argument first made by David Hume and seemingly illustrated by the state of religion in Western Europe that an established church weakens rather than strengthens religious belief, and, a closely related point, that rather than fomenting religious strife (a concern of the framers of the Constitution) it induces religious apathy. Hume thought that religious officials paid by government would act like other civil servants, a group not known for zealotry, because they would have no pecuniary incentive to make coverts or maximize church attendance. That is a good economic argument: if you are paid a salary that is independent of your output, you will not be motivated to work beyond the minimum requirements of the job. A less obvious point is that a public subsidy of a particular church will make it harder for other churches to compete. The result will be less religious variety than if the competitive playing field were equal. A reduction in product variety (with no reduction in cost) will reduce demand for the product.

This point is less compelling than Hume's, because of offsetting considerations. The subsidy may stimulate demand for the established church by reducing the quality-adjusted cost of attending it--suppose the subsidy is used to build magnificent cathedrals or hire outstanding organists and choirs. The increased demand for the services of the established church may offset the lack of religious variety. Moreover, if the subsidy causes the officials of the established church to become indolent, this may offset its cost advantage and facilitate the competition of other sects.

Empirically, however, it does seem that established churches do not increase, and, judging from the experience of most though not all European countries (Poland is a major exception), probably diminish religiosity, consistent with Hume's analysis. However, his analysis is probably inapplicable to the attenuated forms of establishment that are all that are feasible in a religiously pluralistic society such as that of the United States (of course it may be pluralistic in part for Hume's reason).