The authors of model-dependent realism claim that what type of theory may not exist?
Model-dependent realism Model-dependent realism is a view of scientific inquiry that focuses on the role of scientific models of phenomena. It claims reality should be interpreted based upon these models, and where several models overlap in describing a particular subject, multiple, equally valid, realities exist. It claims that it is meaningless to talk about the "true reality" of a model as we can never be "absolutely" certain of anything. The only meaningful thing is the usefulness of the model. The term "model-dependent realism" was coined by Stephen Hawking and Leonard Mlodinow in their 2010 book, "The Grand Design".
Transcendental realism Initially developed by Roy Bhaskar in his book "A Realist Theory of Science" (1975), transcendental realism is a philosophy of science that was initially developed as an argument against epistemic realism of Positivism and Hermeneutics. The position is based on Bhaskar's transcendental arguments for certain ontological and epistemological positions based on what reality must be like in order for scientific knowledge to be possible. While Bhaskar's work is the origin of transcendental realism, it is based upon and further developed by a number of other authors[ref: Collier, Sayer, Lawson, Critical Realism: Essential Readings, etc. The overview of transcendental realism that follows is largely based on Andrew Sayer's "Realism and Social Science".