Scott Alexander uses three fictional stories to illustrate principles of non-empirical scientific reasoning, ultimately applying them to support the many-worlds interpretation of quantum mechanics. Longer summary

This post presents three fictional stories to illustrate important points about non-empirical arguments in science. The first story shows that even when two theories make identical predictions, it's important to choose the simpler one. The second story demonstrates that determining which theory is simpler isn't always straightforward and requires philosophical understanding. The third story ties these concepts to quantum mechanics, arguing that the many-worlds interpretation is preferable to single-world interpretations based on these principles. Shorter summary

Scott Alexander argues that non-empirical reasoning, based on principles like simplicity and elegance, is a necessary and legitimate part of scientific practice, even for evaluating seemingly untestable theories. Longer summary

Scott Alexander discusses the role of non-empirical arguments in science, challenging the view that untestable theories are inherently unscientific. He argues that even in cases where direct empirical testing is impossible, scientists use principles like simplicity and elegance (often formalized as Occam's Razor) to evaluate competing theories. Scott uses examples ranging from paleontology vs. creationism to multiverse theories in physics to demonstrate that this type of reasoning is both necessary and legitimate in scientific practice. He concludes that while there may be debates about the best way to formalize or apply these principles, it's crucial to recognize that some form of non-empirical reasoning is an inescapable part of the scientific process. Shorter summary