  We describe an exploratory and confirmatory factor analysis of the
International Social Survey Programme Religion Cumulation (1991-1998-2008) data
set, to identify the factors of individual religiosity and their interrelations
in quantitative terms. The exploratory factor analysis was performed using data
from the first two waves (1991 and 1998), and led to the identification of four
strongly correlated and reliable factors which we labeled Religious formation,
Supernatural beliefs, Belief in God, and Religious practice. The confirmatory
factor analysis was run using data from 2008, and led to the confirmation of
this four-factor structure with very good fit measures. We also ran a set of
structural equation models in an attempt to determine the causality links
between these four factors. It was found that for the models which provide the
best fit Belief in God does not cause Supernatural beliefs, Religious practice
can cause Belief in God and that there are multiple paths leading to Belief in
God, most of which include Religious formation as a source. The exploratory
factor analysis also led to the identification of other factors related to
traditional values, confidence in institutions and influence of religious
leaders on politics, but these were found to have lower reliability or
insufficient number of items to meet the acceptance criteria, and thus were not
included in the confirmatory factor analysis and the investigation of causal
links. The results obtained in this work have important material implications
for the conceptualization of "religiosity," and important methodological
implications for the scientific study of religion.
