The central hypothesis of the limited enthusiasm model is that a sub-group of church members called enthusiasts, drives conversion growth in the church. Some new converts become new enthusiasts. The Spiritual Life model extends the limited enthusiasm model by allowing enthusiasts to generate spiritual life in the church, which can, in turn, improve their effectiveness as agents of conversion. The analogy is with the spread of a disease, where the enthusiasts are “infected” believers passing the faith on to unbelievers who catch the “disease” of religion. In this model, the infectiousness of the “religious disease” can vary.

See Spiritual Life in Dynamic Modelling for definitions of this concept.

The model predicts a threshold of revival growth that depends on the number of unconverted people in the community and the amount of spiritual life in the church. If the potential for enthusiasts to reproduce themselves is over that threshold, then rapid growth results. The threshold can be lowered if spiritual life is increased, making revival growth more likely and more intense.

This basic model has been extensively revised to include activists.

System Dynamics Model

Unbelievers convert to believers through contact with enthusiasts who have “spread the faith” to them. New converts become enthusiasts. Enthusiasts only remain active for a limited time before becoming inactive and taking no further part in spreading the faith. Inactive believers may leave the church and be open to “re-conversion”, i.e. rejoining the church. Additionally, enthusiasts generate spiritual life in the church, which in turn makes them more effective in conversion. See figure 1.

Figure 1

Growth is driven by enthusiasts, R1, and opposed by the diminishing pool of susceptibles, B1, as in the basic Limited Enthusiasm Model. Additionally, the impact of the enthusiasts is reduced by their limited enthusiastic period, B2. However, an additional reinforcing loop, R3, accelerates church growth as groups of enthusiasts increase in their spiritual life and hence in their effectiveness. It is this variability in the enthusiasts’ effectiveness that is the primary focus of this model.

The growth of spiritual life is opposed by that life fading in individuals, B5. In addition, as spiritual life gets closer to its maximum value, its growth is increasingly opposed by loop B4.

The loop R2 enables the model to have a long-term application and illustrates generational cycles of growth that result from people leaving the church, B3, as in the Demographics Model.

Results of the Limited Enthusiasm with Spiritual Life Model

The model is particularly suited to short, intense periods of growth, as is often seen during a revival. The solutions exhibit the typical steep rise in the growth of a church in revival. Growth stops before the whole community is converted. Such growth only occurs if the reproduction potential exceeds a threshold of revival-type growth, which depends only on the proportion of unbelievers in society. However, if spiritual life is increased, rapid growth is possible even if this threshold is not exceeded. Thus, a stagnant church can become a church with revival growth if enough life is injected.

A rise in spiritual life precedes the rapid growth of the church. Figure 2 shows such a rise in a church where the reproduction potential is inadequate. For the first 7 years, there is very little church growth, but spiritual life is increasing. This is the first phase of the revival, a spiritual change taking place in believers. By around 10 years, the rate of conversions explodes, and church numbers rise rapidly. This is the second phase of the revival, the effect of an enlivened church on the community. Eventually, spiritual life declines and the revival is over. Without any other effects, church numbers decline slowly through deaths and reversion.

Figure 2

There are modes of behaviour where a small change in a parameter can lead to dramatically enhanced growth. Thus, a small change in spiritual life may transform a church’s mission, which can give hope to any church that is struggling and willing to seek God’s help. Furthermore, there is a critical mass of enthusiasts and church size, for which growth is more likely. The model works best for individual congregations rather than a whole denomination unless it is a coherent movement.

See Spiritual Life Results.

This work was part of an M.Phil project pursued by L. Howells at the University of South Wales, thesis Dynamics of Church Growth and Spiritual Life, 2015.

See the revised Spiritual Life Through Activists model.