Heinz Werner formulated an interesting formal heuristic framework for studying the development of psyche. His approach, however, turned out to be relatively unproductive; it could not explain the studied psychic phenomena in general and the mechanisms of change in particular. In this chapter I identified the fundamental shortcomings of Werner’s framework and demonstrated how his formal approach can be transformed into testable theory. Using the reformulated theoretical framework, I showed how it is possible to test empirically Werner’s orthogenetic principle, how and why this principle applies in different domains of psychic development, and how to define criteria for distinguishing the levels of development in different domains. The principles Werner selected for his framework turn out to be very valuable for understanding the development of psyche.