Abstract
Causal loop thinkers are found scattered in several fields. Many of the researchers in the following three fields are causal loop thinkers: (1) General Systems Theories; (2) Operations Research and Management Science; (3) System Dynamics. Within each of these three clusters, there are subclusters. Epistemological differences exist among clusters as well as among subclusters. Conceptual cross-fertilization is rare but desirable. Treatment of heterogeneity varies from cluster to cluster and from a subcluster to another, but is absent among most of the causal loop thinkes.