This document provides an introduction to Multilevel System Analysis (MSA) as a systems thinking approach. MSA uses two keys - perspective levels and cause categories - to analyze problem situations. There are three perspective levels: referential, governance, and transactional. These levels are nested within each other and can be examined separately or together. Cause categories are direct, involving observable causes, or indirect, involving less visible interacting factors. MSA examines problem situations using these two keys to identify root causes and determine the best systems thinking methodology to address the issues.