As contemplative and rational types of generalized thinking, or the results of such thinking, theories are confirmed types of explanation of ways of observations of social reality. Applied to the study of non-profits, they try to explain the "how" and "why" of nonprofits -- how they came about and why they exist.

Helmut Anheier's theories of the nonprofit sector are Entrepreneurship, stakeholder, public good, organizational, voluntary failure, and trust-related. Which theory, in your opinion, most successfully explains how and why non-profits exist. What are the theory's particular strengths? What of its weaknesses, if any?