Sustainable systems must be complex systems. For simple systems, namely those designed for (“optimal”) “equilibrium” pipe dreams, even if in dynamic and stochastic versions, the sustainability issue is meaningless. And complex systems, we will show, need political-economic analysis as well as properly framed complex and adaptive policies to be shaped, structured, organized, institutionally governed, regulated, and managed to become sustainable on a “good” path. We highlight a few examples of complex thinking from ancient times to the present.4 They illustrate that simple (neoclassical) equilibrium thinking is an extreme special case rather than the “normal” in the HET and that “heterodox” (complex and evolutionary) political economy is the way of doing relevant, real-world economics. Much of the HET has included considerations of making embedded socio-(ecological-)economic systems sustainable, both in themselves and in their factual broader (social and natural) environments, through proper framing, structuring, institutional governance, and political regulation. We further illustrate the potential of such “political economy” with an example from evolutionary-institutional economics and its policy implications.