Date of Degree


Document Type


Degree Name





John D. Greenwood

Committee Members

Justin Garson

Peter Godfrey-Smith

Alberto Cordero

Muhammad Ali Khalidi

Subject Categories

Philosophy of Science


fringe theories, fringe science, mainstream science, pseudoscience, demarcation, theory-choice


Fringe theories are a broad set of alternative views that mainstream scientists deny. Case studies from the past two centuries demonstrate that fringe theorists have sometimes been marginalized to the detriment of scientific advancements. While it is accepted that once in a blue moon comes a diamond in the rough, there are far more cases of fringe theories becoming mainstream than has been traditionally acknowledged. Indeed, fringe theories become mainstream with such regularity that our epistemic intolerance towards them is in need of urgent reexamination. With the recognition that tolerance is an epistemic virtue, we can view debates about theory choice with new eyes. While sometimes theory choices are based on theory-laden interpretations of evidence, there are also occasions in which theory choices are made based on logic and competing-theory neutral interpretations of evidence. However, even these commensurable theory choices can be seen to oscillate over time, as novel observations continuously accumulate. I argue that theory choices are in principle never final, which leaves room for keeping fringe theories on the table. Paired with the revelation that theory-entrenchment prevents mainstream scientists from acknowledging important anomalies that are readily explained by fringe theories, this fact suggests that theoretical pluralism is the best route forward for a global epistemic community seeking scientific progress. Theoretical pluralism resolves debates that have long occupied philosophers of science, including the pessimistic induction and the demarcation problem. After considering worries about giving fringe theories space in our current political landscape, I provide a suggestion for carefully putting theoretical pluralism into practice.