Peter Söderbaum argues in his commentary, concerning my article on sustainability economics (Remig 2015), for more open and radical ecological economics. I agree with that statement. However, I reject Söderbaum's interpretation that my arguments foster mainstreamed ecological economics or dictatorship. In my critique of sustainability economics, I raised several issues that have remained unspecified and that potentially lead to unsustainable development patterns, once put into practice. Söderbaum does not reply to these conceptual challenges of sustainability economics. In this commentary, I argue that “structured pluralism” (Dow, 2004) is a constituent element of ecological economics. I welcome Peter Söderbaum's proposal for a discussion about the definition of economics and suggest to rely on Ronald Coase's proposal to define economics as a science that studies the working of the economic system. I conclude that sustainability economics in its current form is closer to neoclassical than ecological economics.