Final answer:
The most basic type of religious organization is the individualistic cult, a term that refers to the least structured and least socially influential religious groups, in contrast to ecclesia which are institutionalized and have significant social influence.
Step-by-step explanation:
The most basic type of religious organization is the individualistic cult. This term encompasses a variety of informal or loosely structured religious groups. In sociological terms, religious organizations can be ordered by their influence in society from the most to the least influential: ecclesia, denomination, sect, and cult. These terms help to categorize religious organizations, with cults being at the basic level and ecclesia representing institutionalized religious bodies with significant societal influence, such as the Roman Catholic Church. It is important to note that many of the major religions of the world, including Christianity, began as cults — considered new religious groups at the start — and evolved over time into larger and more organized institutions.
For example, Christianity began as a small group with beliefs and practices outside the mainstream but transformed into a sect and ultimately became recognized as an ecclesia in some parts of the world. This reflects the dynamic nature of religious organizations and underscoring that the term 'cult' in this context is a neutral description of a religious organization's complexity and societal integration, not necessarily denoting the negative connotations it carries in popular usage today.